Is it okay if I don't tip a delivery guy who called me an asshole under his breath?
Why would you do that?
Because I'm an introvert and he's a free spirit....
I can understand your frustration with that delivery person, but I think it is customary and well-mannered to tip a delivery person nonetheless. You should consider perhaps switching to a different delivery company, because if you treat this person badly, they can damage your packages in the future.
That delivery guy was a jerk.
Tipping is a social norm here in the US and if you don't, could be seen as being rude. However, you still have the right to refuse to tip if the person is being rude themselves or doesn't get the order right. It is up to you based on the given scenario.