I agree - this letter should be as un-confrontational as possible. Save the confrontational stuff for if they still say no, if you want to.

But I would advise you not to make a fuss even if they say no. You have to pick your battles. To me, it wouldn't be worth it. You can wear trousers, it's not that big a deal. But if you create a fuss, they could really make things difficult for you.