Tell that to the single moms in my restaurant who barely make ends meet.
Not my job to meet their ends.
Whether or not the waitperson in question is a single parent would seem to be irrelevant to the arguement- unless you're arguing "from each according to his ability, to each according to his need" at which point tips wouldn't be calulated based on the quality of service provided as a fraction of the total bill, but on some calculus of how many dependents the waitperson has.
"Tell that to the single moms in my restaurant who barely make ends meet."
Well Boo Hoo Hoo, they get special consideration because they managed to reproduce? "You birth it, you own it," don't come whining to me because you got knocked up or chose to procreate with a loser.
I hate to ask the obvious, but why don't you raise your prices and pay them more if you're so concerned?
"Tell that to the single moms in my restaurant who barely make ends meet."
Maybe you should raise your prices and their paychecks by 20% ?
Why don't you pay them more? Why aren't you paying them a "livable wage?"