One of the easiest things to do is pass judgment on other people. Especially in this day and age of advanced technology, with a quick snapshot or article here and there, it's very easy to judge others without knowing the whole story. Accurately judging a person is one of the most difficult things to do. It takes a great deal of time and research to objectively analyze another person's overall behavior. That's why most people take the easy way out and only judge what they see; too much effort is involved in doing otherwise. However, the only way to really know another person is to judge them by the totality of their actions.
There is a misnomer that we aren't allowed to judge people, but that isn't the case. As Jews, we are allowed to make moral judgments of behavior; we just aren't allowed to knit-pick at every little thing other people do. For example, if you know a fellow Jew who lies, cheats, steals, or hurts others in some way, you can - and should - call them out on it. However, if you simply disagree with how they dress, their denomination, outlook on life, or political affiliation, it doesn't necessarily mean they have bad character. We can disagree all we want on the issues of the day, but we must always uphold a high level of interpersonal decency.
A good thing to keep in mind is the principle stressed by Rabbi Akiva, Hillel, and many others - to treat others in a manner that reflects the way you would want to be treated. Before making a character judgment of another person, first think of whether or not it's a fair analysis and if you would want to be judged in the same way. As it says in Pirkei Avot (1:6), "havei dan et kal ha'adam l'kaf zechut" - judge everyone favorably (i.e. give them the benefit of the doubt). "Et kal ha'adam" literally means the whole person. We are only able to accurately judge someone when we know the totality of their character. We may only see the negative, when in reality, they do a lot of good deeds in private without our knowledge.
Nevertheless, we don't have to know every detail about each other's lives. In fact, unless you're dealing with your spouse or young children, it's usually best not to know every detail about someone else. As Chazal (our ancient sages) teach, we are judged in the Heavenly Court according to the way we judge other people here on earth. It's another instance of neged k'neged midah, measure for measure; it applies for good just as it does for bad. When we do our best to judge others favorably, we are actually helping ourselves in the process.
God is often depicted as a father who cares for His children. For example, we say on different occasions throughout the year, "Avinu Malkeinu" - God is both our father and king. Just as a parent doesn't take kindly to their kids being harassed, neither does God like it when we demean each other. As mentioned in a previous post, there is a tremendous lesson to be learned from the symbolism of Keruvim (Cherubim), which were mounted upon the Aron HaBrit, the Ark of the Covenant:
While each figure had its wings rising toward heaven - representing our relationship with God, the faces on each figure were looking at one another - representing our relationship with other people. The message is that while each one of us engages in our unique service of God, we must always remember to act decently toward others while they do the same. In addition, the Shechinah (God's presence) rested upon the Keruvim. If this doesn't show how important God regards our treatment of other people, I'm not sure what does. If we are ever to merit the return of the Shechinah, we must be good to each other. The two are inextricably linked.