[vorpalhex]

A compliment or a question is usually a good way to start. "Oh hey, nice shirt, have you seen that band in person?"

[jamesmp98]

lol I went to a local music venue a few weeks back and tried this. After inquiring about one guys shirt, he started at me for a few seconds like I was insane and turned around

[res0nat0r]

If someone at a concert acts like you've insulted them by asking about their music related shirt, then the problem is with them, not you.

[throwayEngineer]

This is precisely why I don't feel bad about asking innocent questions.

If they can't handle basic conversation, it's them.

[vidarh]

Then you have the perfect opener for anyone overhearing by cracking a joke about it.