Not a lot of interpretation to no alchoholic or sexual t's allowed. I suppose you could argue double entendres but the fact remains this is not a narrowly tailored rule.
My problem would be t-shirts with a political or religous message. A shirt that says "support our troops" could not be allowed if a shirt that says "not my president" was banned. It is best just to ban all of them outright.
You're too young to remember the 50's......LOL....when rules were RULES! And, the adults were in charge.