You have 2 choices: You either suck it up with a smile (or condescending giggle, in your case lol), or, you quit and move on to another job. That's basically it.
Unfortunately, that's the cold hard truth when you deal with the public. Yes, your manager should have said something, or put a different server on their table. Nobody should be treated like that in the workplace. However, when you deal with the public, you're going to deal with idiots of all kinds. You either have to learn to handle them, or get a job that doesn't involve dealing with the public.
