Every restaurant I've ever eaten which had "forced tipping" (usually for parties of 6 or more) a manager will remove it if you've had poor service.
As a former waitron, I can tell you that the number of people who are clueless about tipping is staggering and it gets worse when there's a large table as people usually sit there and figure out what they owe WITHOUT putting in the tip.
Not to mention most waitresses and bartenders make $2.01 an hour and they have to pay taxes on 8% of their sales even if they don't get tipped 8%.
Again, if the "forced tip" is more than you think is deserved, talk to the manager.
