I was saying that there are times that it happens that have nothing to do with skin color and would happen (maybe the waiter is having a bad day who knows) to anyone.
Like the man in the car next to me (assuming he is not gay) if I was a hot girl I would automatically assume it's because I'm a hot girl. Of course this is not the same as saying that men don't look at a girl in the car next to them!
Of course that's a possibility -- servers have bad days, sure, but these isolated incidents don't negate the need to solve the bigger problems of wage disparity in restaurants (cooks being paid half what servers earn -- close to minimum wage in some instances, no matter that they went through culinary school and incurred huge debt), the problems of racism and sexism, etc. I feel non-tipping is the easy and obvious solution here.
I think that is a bit of a stretch. There is concrete evidence that explains this happens a lot, and it's clear that racism [1] and sexism [2] are a key part of it.
And -- not as scientific here -- but there's intuition I have gathered that's backed up with 10 years of extensive dining out in various arrangements and settings, and anecdotes from my server friends about the politics in restaurants.
[1] http://tippingresearch.com/uploads/Business_Considerations_T...
[2] http://tippingresearch.com/uploads/ServerAppearance1-3-08.pd...