Why do we judge others?

I often ask this question to myself..Almost everyone I know that watches "LOST" automatically hates Michelle Rodriguez's character Ana Lucia. I think often times in life we judge people without knowing the whole story. I did this recently with one of my neighbors. She's a bit crotchety, but then I found out she's alone, has cancer, etc. So I've learned to try to be more kind to people in general. Its not easy sometimes especially when they act like monsters, but we all have our days.