I saw that R. Yehuda Henkin (Hibah Yeseirah on Numbers 13:31, in the back of Bnei Banim vol. 2 p. 67) has a very interesting insight into the story of the Spies. The Spies returned from touring the land of Israel and reported to Moses and the nation (Numbers 13):
27 Then they told him, and said: "We went to the land where you sent us. It truly flows with milk and honey, and this is its fruit. 28 Nevertheless the people who dwell in the land are strong; the cities are fortified and very large; moreover we saw the descendants of Anak there. 29 The Amalekites dwell in the land of the South; the Hittites, the Jebusites, and the Amorites dwell in the mountains; and the Canaanites dwell by the sea and along the banks of the Jordan."R. Henkin points out that even after reporting both good and bad about the land, and after Caleb's opposing interjection, the Torah (v. 31) still refers to the Spies as "anashim" (men). Rashi, on 13:2, explains that the word "anashim" (men) implies importance: "Anashim in Scripture always refers to distinction. At that time they were righteous." Since, even after giving their report, the Spies are again called "anashim," by implication they were still righteous at that time! It was only afterwards, when they gave their opinion that the nation could not conquer the land and then exaggerated (or lied) to support their viewpoint, that they sinned by giving a "bad report."
30 Then Caleb quieted the people before Moses, and said, "Let us go up at once and take possession, for we are well able to overcome it."
31 But the men (anashim) who had gone up with him said, "We are not able to go up against the people, for they are stronger than we." 32 And they gave the children of Israel a bad report of the land which they had spied out, saying, "The land through which we have gone as spies is a land that devours its inhabitants, and all the people whom we saw in it are men of great stature. 33 There we saw the giants (the descendants of Anak came from the giants); and we were like grasshoppers in our own sight, and so we were in their sight."
Their offering of a balanced report and even their honest evaluation of the possibility of conquering the land was not sinful. It was their subsequent exaggeration to support their point that was their sin. Gathering intelligence is allowed. Honest reporting of the information is permitted. However, analyzing the facts in anything other than an entirely honest fashion is a great sin.