Saying people are bad tippers isn't bad at all, especially if it is telling the truth. I'm all for the whole tipping isn't a mandatory thing, but mostly because I live in Canada where people are paid a living wage without the needs for tips, most of the time.
Certain jobs are different, one of which are delivery driver jobs where people's main source of income is tips, and then you also have to take into account things like gas, car maintenance, etc.
NGL dude, your comment to Dal came off as major dickish. The bottom line is people have the right to complain about whatever they want. I can complain about how my computer chair took an extra week to get in, and Dal can complain about bad tippers or whatever else that pleases him. Just because you tell someone to "Stop Complaining" doesn't mean that they have to, nor does it mean they should.