No one must stand for the anthem. Or salute the flag. Or put hand over heart. Some people consider those respectful actions.
If somebody wants to make a statement, so be it, because, you know, there’s that wacky First Amendment that protects it.
(Hey, can we go all Antifa and make disrespecting the flag “Hate Speech?”
If we do that, we’ll get all kinds of support from our betters, since Hate Speech is banned in the First Amendment…I jest, I jest…)
But if you have religious convictions against gay marriage? BAKE THE CAKE.