Young polish dude love to fight (but they're generally bad at it too - just egged on by friends to show their worth) and generally negative towards people who aren't Polish looking. Don't be surprised if drunk idiots try to get him to fight them with aggressive posturing and statements. That said, there's cameras everywhere and it's not worth tangling with them on the off chance you find someone who's good, or there's weapons that get involved.

Better solution is to just walk away if/when the situation occurs. (It will happen at least once during his stay, I'm sure)

Look at what happened in Bolesławiec. Polish Army Officer made racist comments to a black US soldier, US soldier didn't walk away and instead allowed Polish Officer to escalate the situation. They fought and the Polish Officer was sent to the hospital in critical condition. It became an international incident. The US Soldier easily won the fight, but the trouble wasn't worth the trouble.