This wasn't my experience. I got tipped well because I gave great service even when I knew the table wasn't going to tip. It's just easier to give consistent service then to pick and choose which table gets good service and which tables don't.
Indians were cheap and Black tables gave the most problems. Sending food back, asking a million and one stupid questions, not reading the menu and ordering shyt we didn't even serve, nasty attitudes...just a pain in the ass. Not all of course, but enough that servers in general get pissed when they get Black tables.
When my husband and I go out we tip well. Who the hell cares what the waiter look like, we're there for the food and our attention is on each other. As long as the waiter looks clean and doesn't smell I don't really pay attention to them.
Blacks and the ridiculous reasons as to why their cheap asses don't tip.