Always treat everyone equally and like decent human beings(or something else if you consider yourself something else). It's rude to outright attack, come at, or berate someone for no reason.
Decency is hard to come by now a days. When you experience the opposite of it first hand, just makes you shake your head and ask why.
When you don't do this you come off as brash, insulting, and arrogant.
Happy holidays!