[PrettyBoy]

Originally Posted by Senusret I

If you can't offer them a plain replacement t-shirt, there's nothing you can do as a gentleman.

Exactly. Senusret, I agree.

The same thing happened to me my sophomore year in college. I hadn't been a member of my fraternity for more than 4 weeks. I was still very new to greek life. I saw a girl on our campus with a Kappa Founders t-shirt on. She didn't go to our school. She attended Ohio State. I asked her where she got the shirt and she told me a friend of her's gave it to her who was not a member of the fraternity. She said he wasn't even from this country. I asked her would she take it off if I gave her my shirt? She said no. I left and told another brother and he tried to get her to take it off, and she still declined. Of course he offered her another shirt, but she said no. We explained to her what could happen to her if she continued to wear the shirt. We told her not every member is as polite as we were being to her. Well, to make a long story short, she left the campus and came back about 3 hours later to our relief with a different shirt on.

To the OP if it bothered you that much, I would have just tried to explain to them why it needs to come off, and if they said no, then there's really nothing you can do about it.