When I was a young boy, whenever I got into a spat with one of my brothers, we'd start calling each other names. My mother would break us up by saying, "Don't call people names; it takes one to know one."
It didn't mean much to me back then, but the older I get, the more I realize that she was right.
I started noticing a trend. It was always the fat person in our group who would call some stranger fat. Always. It was always the biggest slacker at work calling someone else lazy. It was always the most truth-challenged individual calling someone else a liar, etc, etc.
This is true with any number of human faults we can think of. Why? One Eastern philosophy claims that the outer world is, in fact, a reflection of our inner world, and that when you pick out a shortcoming in someone else, you are, in fact, recognizing it within yourself. This is a little heavy, but there does seem to be a connection of some type.
Try your own little experiment at work, at home, on your softball team...anyplace where you will be with a group of diverse people. Note when someone starts talking about someone else. Does that person have the same fault that he/she is picking out on someone else?
You might be surprised.