Hopefully I won't be judged for quoting an answer from 'Yahoo Answers' as a response (yeah right), but it sums up how I feel about the whole judging thing, and the author has worded it much better than I could manage at this time of morning (3am here)
"Judgement is born of ignorance. What I mean by that is that it represents our assessment of circumstances and events based on incomplete information.
It's not so much that it is plain human nature to judge, as much as it is that we cannot possibly know everything about all circumstances and events; therefore, we must make judgements based on our incomplete information.
When a judge presides over a case in his courtroom, he is functioning in ignorance of the circumstances and events under scrutiny. He must depend on the information provided to him by the people who actually know what happened or think they know what happened, in order to make any kind of decision on the case.
And, when we sit in judgement of others, it is because we are not inside their heads. We do not know the circumstances and events that influenced that person to think, say, or do what they thought, said, or did. For if we did, we would have likely done exactly what they did.
The best that any of us can hope to do is analyze the circumstances and events of others in the context of our own - but, they aren't the same. We each have our own individual circumstances and events that guide our choices in life. And, just because the circumstances and events of my life did not lead me to do what you have done does not mean I would not have done it, if I had experienced what you have experienced.
So, our judgements, born of ignorance, will often steer us in the wrong direction. That is why they should be avoided as much as possible.
And, there is really nothing we can do about it. For reality is made up of an infinite number of different possible perspectives and we have but one - our own."
lifewhispers1 (Yahoo Answers 2009)
As a very superficial example of this (all I can manage at this stage) is the muffin top, mentioned in a previous post. If I were to see someone with a muffin top, although I would not consciously choose that look for myself, who is to say whether or not the person with the muffin top has recently lost a lot of weight, is over the moon that they can fit into a pair of jeans, and think they look great. Who knows, and good for them regardless.
I'd say I judge judgmental people, but then again, I don't know the circumstances that made them so judgmental in the first place, so, as long as no one is getting hurt, I do try not to judge.