My view: Standing for the National Anthem is not mandatory.
I stand for it, hold my hand over my heart and sing it.
But I'm not African-American, whose ancestors were brought to America on a slave ship, and mistreated and treated like non-persons (except when it came to counting voters, then they were 3/5 of a person who couldn't vote). I'd be pissed, too, if my ancestors were treated that way. And my ancestors were not on slave ships, but departed from Italy and Poland.
The First Amendment applies to everyone, whether we agree with them or not. They have a right, in making a statement, to kneel or raise a fist. Everyone else has a right to disagree, or stay away from the games, which NFL fans will not. They will just blow smoke in anger and then go back to watch their favorite teams. It's the nature of sports fans.
If you start deciding who does NOT have Free Speech rights, then we're all in trouble. That's how Hitler got into power. First the Jews, then anyone else who disagreed with him.
The First Amendment means someone I do NOT agree with has a right to voice his opinion, as long as -- as the Supreme Court ruled -- he/she does not yell "Fire!" in a crowded theater when there is no fire.
Democracy is messy. So we have to let people we disagree with have their say, too, as long as it doesn't incite violence, as Trump's rhetoric did. Trump still has that right to stir up racial and ethnic hatred but then Trump, like every citizen, is responsible for what his free speech leads to. If it incites violence, then it's on the person whose speech incited the violence.