Why do folks judge so harsh???

I was in the store the other day and i had my young black and educated t-shirt on...well on the front it said "Americas Worst Nightmare"I guess that kinda through the lady off for a minute...who knows. anyways...i proceeded to ask her for some help and she actually seemed scared and kinda turned away from me. then i turned around and showed her what it said on the back and you wont believe what came out of her mouth next...."oh I'm so glad that is what it said, i thought you were one of those thugs or something"...then she proceeded to help me...keep in mind that she was black as well. now i wasn't in there all thugged out with my grill in or wearing a du-rag or even saggin'. i guess the first appearance of the shirt just made her judge me. i was being my usual nice, charming self, and meant no harm....now here is the question, do you think that was wrong of her to judge me off appearance alone, or was it simply the fact that i am a young, black male and i looked intimidating? is it fair to judge others off looks alone period? i just wanted to share a very small chapter in my life with you guys...if u care to comment or write back, holla at me on any occasion...