It's pretty clear that the maintainer should've handled it better but I'd be lying if I said I never felt like telling a petulant user off. The problem is he didn't handle it professionally.
Leaving that aside, even if you diagree with it you (the user) are not entitled to anything, especially not entitled to have an attitude.
Just think about it differently, what do you think would happen if you do the same in the real world?
I'm pretty sure in the best case scenario you may be asked to leave and in the worst case scenario you may be "escorted" out of the premises.
A little bit of politeness goes a long way.