A bribe is paid before the fact; a tip is not. I suppose you could call it a reward, of sorts, but it's not a bribe. (And I do agree it should be lessened or not paid for poor performance, just like a garment with a tear should be discounted or refunded.)

Why, then, do you support government health and safety regulations? Why not let the free market decide? If employees don't like the safety protocols at a particular place, they can find a new job.

And, similarly, what employers do with customers is also a free market issue, and an employee's contract is with his employer, not the customer; why then, do you feel it is inappropriate for employees to give poor service to customers when they are upset with the employer? Why shouldn't they be free to do as they please, since the customer can simply go someplace else?

(And, again, I support your position on these last issues... but it seems to disagree with your position on the free market vis-a-vis tipping.)