It amazes me that people still don't know the difference between stereotypes and racism. Racism is hating another person because of skin color or thinking your race is superior to others. Stereotyping is ideas held about an entire group because of certain members of the group and it can be positive or negative.
Onto the black guy getting watermelon, who cares. Because he asked for watermelon like that, it makes it funnier than it would have been if he just asked where the watermelon was. I know black people that follow the stereotype, because the tend to be true for some unknown reason.
My cousin had a neighbor that was black and he didn't want anyone pushing him underwater in a 4 foot pool, and he was at least 6 feet tall. Then the resident black kid at my school (we have only one at a time, I think its a rule or something) asked for other people's watermelon the one day it was served, which made everyone laugh.
Laughing at people because they fall into stereotypes doesn't make you less human, in fact it makes you more human. When I see stereotypes being followed through, I laugh and point it out to as many other people as possible so they can join in with my enjoyment.