You'de be amazed.
I've seen some horrid acts get great croud response just because they played some Greatful Dead tunes... very badly, but still- They played the croud's thing.
Most people aren't musicians, so they're just there to be entertained- so if you're entertaining, they're happy. Mayve every musican in the place is sayin "Phhbbbt- poser punk" (or whatever), musicians listen to music and judge bands differently than "normal" people.