Yeah, sounds like you dealt with a butthead. It's totally fine to prefer 3.5 to 5E, or Mutants And Masterminds to Powered By The Apocalypse, or FATE to GURPS, or whatever. What's NOT cool is to crap on someone else for liking something else.

I haven't seen much hate for 5E, though-I've seen plenty of people assuming it's just as unbalanced as 3.5, but that's usually ignorance, not malice.