What do you think of me wanting to snap someone's credit card in two?
What made you want to break their credit card?
Because he was giving me odd looks
It can be uncomfortable when someone looks at you in an odd way, but breaking his credit card really isn't a great way to respond. That will only anger him and make the situation worse. Instead just ask him if there's a problem you can help him with.
I don't think people care about their credit
Breaking someone's credit card is wrong and will lead to tension and conflict between the both of you.