The eternal struggle: The guitarist whose amp doesn't sound good unless it's turned up loud vs. the sound guy who wants him to turn the amp down so he can run it through the monitors

Sounds like workplace related hearing loss to me. I SAID SOUNDS LIKE... you get the idea.

sometimes guys would have you "sidewash", point the amp sideways across the stage instead of pointing it at the audience

Just don't put the amp through the PA if it's too loud

I'm always on the side of the guitarists with this, but then I would be