I don't see why not.
USA is a shitty country that has done plenty of shitty things to the world. Respect is earned, it's not free. If someone doesn't like the history and what that flag represents, they are free to disrepect it.
You don't get a fucking "disrespect-free" right on something just because it's a flag.
Your lack of respect is the issue. You may use your freedom how ever you wish. But if you think taking a piss on the flag just because it ain't illegal is "fine" well then... I guess we have nothing further to discuss, I know all I need to know.
No, the issue is blind respect.