Trying to convince you to dress up on any sort of moral basis is out of the question. So I'll try it a different way. If you're going to a mosque or some worshipping place of another religion, what do you do? By all standard conventional wisdom, you do as the proverbial Romans do. Respect the customs & traditions of the place you are entering even if you don't agree with it. Otherwise, don't go.
I would NEVER attend any place of worship that denied Jesus Christ.
Why? Do you think God would be angry?