When you think about it, the clothing you wear is a form of expression and, as long as it is not obscene, is protected by the first amendment. You don’t need a good reason to do it because you have the right to wear what ever you want regardless. The only restriction on this type of first amendment activity is that you can’t use it to engage violence, harrassment, or public obscenity. So if anyone wants to harass you for what you wear, tell them the first amendment of the US constitution says you can wear whatever you want regardless of your gender.