That is really sad.
I'd lay $$ down it was due to your skin color. I feel that most prejudiced reactions in cases like this are due to fear out of lack of exposure to other races and cultures. Those idiots would rather sit in the desert heat for hours than take the aid of someone that looks different than they do. That is not only stupid, but sad. :hammerhea I feel bad for their ignorance.
I hope you do not let that dissuade you from helping others in the future. I have a feeling it won't.