I honestly don't tip anyone unless they actually do an exceptional job. Hell they get paid to do whatever it is they're doing in the first place, why should we tip them?
I understand it's a different culture in the states, but personally I find tipping ridiculous if you start giving YOUR hard earned money to people who are already getting paid, just for doing their job.
I think some of the statements here have not been worded as well as they could, it's like saying ALL muslims are terrorists. Or ALL imigrants start trouble, it's a rash generalisation. I have a feeling that the point that was being tried to get across was 'MAJORITY of non tippers are black' - if in fact this is the case, well, then there's a question to be asked after it.
Like here in Aus, not ALL refugees start their own gangs, and terrorize people, but it is in fact MAJORITY of violent gangs and related crime, is CAUSED by these people.
Hope that's clear enough 