Only times it's considered acceptable to not tip is when the server has been rather rude (check your behavior as well and make sure you didn't/don't provoke it) or has done a very poor job (even then, consider how many people they might be having to serve, quite often you are not the only customer and employers will overwork staff).
lol...what the shit is that
He's probably a food server
Yup. Only servers or former servers have that level of entitlement to them.
It's not entitlement. It is being aware of how the world works, and in the service industry, there are often things outside of your control that the asshat public blames you for.
Factors out of your control aren't exclusive to being a waiter. Only waiters feel entitled enough to suffer their customer base for it.
