So? The US isn't a fascist dictatorship. There's nothing wrong with disrespecting the national anthem, it's just propaganda. Free speech is a more important American value than blind patriotism.
Which is why he didn't go to jail.
> There's nothing wrong with dis respecting the national anthem
Sure, it isn't illegal, but that doesn't mean individuals can't be offended by it. To many, the national anthem carries significant meaning.
There is lies the whole point of doing it. If it was meaningless to people it would have no impact as protest.