Rabbenu Yonah (Sha'arei Teshuvah 1:18) has an important comment about how we look at others. He says that it is the way of the righteous to notice the good qualities in others, presumably even the wicked, while it is the way of the wicked to always criticize other people. Here is R. Yaakov Feldman's translation, as posted to the blog Der Alter (link):
When King Solomon spoke about tshuvah he cited this trait specifically. He started by saying, “When the righteous rejoice, there is great honor; but when wrongdoers arise, people are sought out” (Proverbs 28:12). Which means to say that the righteous honor and respect people for their good qualities, while wrongdoers always look for faults in others and mistakes in order to disparage them, even after those people would have rejected what they had done, and did tshuvah.Something to think about in our reaction to other people.