I saw the following story posted on a website:
[The CHazon Ish said] "anybody who says that there is in CHazal even one thing that is "laav davka"("not exactly true") , is "mekatzetz b'netiyos" . . . he would even refrain from eating chicen that was slaughtered by an expert and skilled shochet if he was one of those people ...I believe this story to be either entirely untrue or missing important background that significantly changes the story's meaning. R. Binyamin Yehoshua Zilber, in his Responsa Az Nidberu, frequently warns people not to believe stories they see and hear about the Hazon Ish. Based on the following, I seriously question the above story.
The CHazon Ish used to say, that someone who has warped hashkofos, is worse than someone who violates shabbos, regarding making his wine into yayin nesech. Rav S. Greimenam ZTL testified thusly in the name of the CHazon Ish, and added an incident that happened when the Chazon Ish was in Vilna. There was in those days a young man, an outstanding lamdan, that would stay by the Chazon Ish. Every Firday, he would bring the CHazon Ish a bottle of wine. He used speak a lot with the CHazon Ish in learning. Once, they were discussing a Chazal about Og Melech Habashan who uprooted a mountain to throw it on the Jews, and a miracle happened ... the young man commented: This is probably said as an exaggeration and a figure of speech. The Chazon Ish gave him a look, and said sternly: "Next SHabbos, do not bring with you any wine!" ...
"Casting doubts on the truthfulness of certain words of Chazal is like "giduf" against chazal. Someone who veers from this is, as per out tradition, like a Kofer in the words of Chazal; his shechita is trief, he is disqualified to be a witness etc."
The implication of the story is that anyone who does not believe every Aggadic statement in rabbinic literature literally is a heretic. It could be that the background behind this story is that it occurred in a time and place where people would frequently leave Orthodox Judaism over such matters, so that questioning whether an Aggadic statement is literal really implies deeper theological doubts. However, taken at face value, it is virtually impossible for someone familiar with rabbinic literature to declare someone to be a heretic for questioning whether Og literally uprooted a mountain and threw it at the Jews.
The Rambam, in his Commentary to the Mishnah, Sanhedrin, introduction to chapter Helek, lists three types of readers of Aggadic material:
The first class comprises the majority among those that I have come across and whose compositions I have read and of whom I have heard. They understand the word of the Sages literally and do not interpret them at all... They only do this because of their ignorance of sciences and their being distant from (various) fields of knowledge. They do not possess any of the perfection which would stimulate them (to understanding) of their own accord, nor have they found someone else to arouse them. Therefore, they think that the intent of the Sages in all their precise and carefully-stated remarks is only what they can comprehend and that these (remarks) are to be understood literally... This class (of thinkers) is poor (in understanding) and one should pity their folly. In their own minds, they think they are honoring and exalting the Sages, but they are actually degrading them to the lowest depths. And they do not perceive that. As God lives, it is this class of thinkers that destroys the splendor of the Torah and darkens its brilliance...In no uncertain terms, the Rambam states that it is wrong and even offensive to understand every Aggadic statement literally. This attitude continued for centuries and was repeated in many different works. I have no need to quote from obscure works because this attitude is so prevalent that it is in books that occupy most home libraries. This was the approach of the Maharal, the Ramhal and, of course, the Vilna Gaon. There is a famous story about R. Yisrael Salanter in which he explained the allegorical nature of Aggadah through a parable about a newspaper story in which current events are referred to in easily understood idioms that are, to the outsider, entirely incomprehensible. The approach continues to our day, when R. Eliyahu Dessler, a respected colleague of the Hazon Ish, regularly lectured in that vein in the Ponevezher Yeshiva in Bnei Brak, as demonstrated in his Mikhtav Me-Eliyahu. His student and successor, R. Hayim Friedlander, continued in that path, as can be seen in his Sifsei Hayim. More recently, R. Aharon Feldman, currently the rosh yeshivah of Ner Yisrael in Baltimore, published a book titled The Juggler and the King: An Elaboration of the Vilna Gaon's Interpretations of the Hidden Wisdom of the Sages in which he expands the Vilna Gaon's Aggadic commentary of many Talmudic and Midrashic passages. R. Feldman writes in his overview (p. xxii):
(Fred Rosner, Maimonides' Commentary on Sanhedrin, p. 140)
[I]n Aggadata the message - often some of the most basic ideas of Judaism - is garbed in what appears to be parables, riddles or even practical advice without apparent religious content. In line with this, one great authority writes that the above-mentioned dictum, that a verse never departs its plain meaning, applies only to the Torah's verses and not to Aggadic statements; in fact, he writes, the plain meaning of Aggadata is usually not its true meaning.Even though it is not necessary, since I have before me the galleys of the soon-to-be-reprinted The Students' Guide Through The Talmud, an English translation of the Maharatz Chajes' Mevo Ha-Talmud, let me quote from his chapter 17 (p. 142):
Now since the style which the Rabbis adopted in the Midrash and Aggadah is not understood by the average student, so that at first glance many strange idioms and extravagances appear to be contained in their statements, such as have afforded the critics opportunities to pass censure upon them..., I have set myself the aim to show the reader the methods employed by the Rabbis in these subjects, and to explain the many categories and definitions as well as the idioms and modes of expression which are used by them in the Aggadah...Now, going to the specific midrash discussed by the Hazon Ish, it can be found in Berakhos 54b (I am using the Soncino translation out of laziness):
'The stone which Og, king of Bashan wanted to throw at Israel'. This has been handed down by tradition. He said: How large is the camp of Israel? Three parasangs. I will go and uproot a mountain of the size of three parasangs and cast it upon them and kill them. He went and uprooted a mountain of the size of three parasangs and carried it on his head. But the Holy One, blessed be He, sent ants which bored a hole in it, so that it sank around his neck. He tried to pull it off, but his teeth projected on each side, and he could not pull it off. This is referred to in the text, Thou hast broken the teeth of the wicked, as explained by R Simeon b. Lakish. For R. Simeon b. Lakish said: What is the meaning of the text, Thou hast broken the teeth of the wicked? Do not read, shibbarta [Thou hast broken], but shirbabta [Thou hast lengthened]. The height of Moses was ten cubits. He took an axe ten cubits long, leapt ten cubits into the air, and struck him on his ankle and killed him.We are obligated, the story from the Hazon Ish implies, to believe that this literally happened. Og actually uprooted a mountain and tried to throw it at the Jewish people. Anyone who does not believe this literally is, evidently, a heretic.
However, anyone who looks in the standard commentaries will find that they did not interpret this literally. In fact, the Rashba, cited in full in Ein Ya'akov, took this passage as an opportunity to explain at length his allegorical approach to understanding Aggadah. The Rashba explains that the mountain symbolizes the patriarchs, and that Og was hoping to defeat the Jews with the merit he had acquired by assisting Avraham. However, with the combined merit of Moshe, the Jews and the patriarchs, they were able to withstand Og's merit.
Now, even if one were not going to bother ab initio looking in the Rashba or the Ein Ya'akov, once the Maharsha - the standard Aggadic commentary printed in the Vilna Shas - quotes it you probably would. The Maharsha, however, disagrees with the Rashba and explains it with a slightly different twist, albeit equally allegorically.
Additionally, no less an authority than the Noda Bi-Yehudah, in his Tzelah commentary on the Talmud, suggests a non-allegorical but also non-literal explanation in order "to bring the words close to the intellect and to nature." He suggests that Og had a big rock that he was planning on throwing at those few Jews who were carrying the Ark of the Covenant. He was a strong man and that was an unusually big rock, which is why it is so significant. However, unlike the Rashba and the Maharsha, the Noda Bi-Yehudah believes that there is a literal core to this exaggerated historical story.
To sum up, it is hard to believe that the Hazon Ish said that anyone who believes that an Aggdadah in the Talmud is not meant literally is a heretic. He surely knew what the Rambam wrote and, more importantly, what the commentaries on that very passage had to say. The story is either untrue or missing important information. Furthermore, it is misleading to tell such a story in public because it gives the incorrect impression that one must understand Aggadah literally. That is simply not the case.