ALL blacks tipped considerably lower?
did ALL whites tip considerably higher?
you're making sweeping generalizations and ignoring the imbalance of one race versus the other in lower socio-economic brackets (a point which exactly zero members of the blacks-dont-tip squad have yet to actually address.)
rocknrolla actually touched on it by saying blacks in nice neighborhoods tipped poorly and non-blacks in poor neighborhoods tipped well.
dunno... I've heard stuff like this before. I have no problem with *people* who have tip poorly getting poor service, but it's basically just a cycle that if you treat someone who has never eaten at your place poorly because of how they look, that will cause a lower tip, and so on...