Middle-class blacks already have a reputation as lousy restaurant and taxicab tippers (actually, non-tippers). When I managed a seafood restaurant on Martha'a Vineyard 15 years ago, the only black customer I saw all summer was a middle-aged dentist with his wife and, I believe, two teenaged daughters. The waitress serving the party was the sweetest girl on the staff, very capable and very experienced. The dentist, who was threatening to walk out on a $100+ tab, drove the waitress to tears. I had to take over the table for her. I got the man to concede that the food was good (Was everything alright? "Yes" -- it's psychologically important), was forced to waive the charge on his expensive appetizer for free (four orders of baked, stuffed clams or something comparable to it), and, it goes without saying, he left no tip. The sullen expression his wife was flashing him made it clear that this was not an isolated incident.
A couple of years ago, one of the few New York cabbies who had the cojones to write about why he looked on young, black male riders with trepidation, was because that group had an extraordinarily high rate of running out of the car at their destination without paying. As you can imagine, the driver caught hell for his honesty.
An increasing segment of black society insists on getting something for nothing. The funny thing about the story you retold, is that spitting on food or in beverages destined for customers of another race is a tradition among some black racists, but not to my knowledge among whites. You'll recall Jesse Jackson's boast of having spit on white customers' food when he was young and worked in some service capacity. The characters in the story were thieves who never planned on paying for their meals.
I have it on good authority that this is also true in the cosmetology business. It's been said that most ill-tempered threats of litigation come from blacks - usually for some ludicrous variant of perceived racism - as do excessive demands that vastly exceed the norm. Of course, there is little to no tip in most cases.