The problem is that what is or is not offensive is a matter of opinion. When rules are not concrete and instead left up to the interpretation of the enforcer, problems always arise.

It is a private company and their dress code stands no matter what someone thinks it's their right to wear. It's like going to a 5 star restaurant with flip flops on, they can and will turn you away and there is nothing you can do about it. Like I said, the thing that causes problems here is interpretation, tons of people wear t-shirts on planes.

I couldn't care less if that guy wears that t-shirt. It's his shirt and has nothing to do with me.