As tempting as it seems to wear tennis shoes with your tux, don't do it. I think it looks ridiculous. If you're 14 years old, maybe give it a shot. In general, don't portray anything that says 'I'm too cool and I don't care.'
No other offense has ever been visited with such severe penalties as seeking to help the oppressed.
It's sometimes the random people that say things that aren't so nice, but that's okay.