Few things.
One, one of those Americans chose to ram a car into a group of people also exercising their Constitutional right to protest. Ramming a car into a group of protesters is not protected by the Constitution.
Two, Trump is being called out for expressing his opinion. Trump also exercised his Constitutional right. It does not absolve him from consequences, such as people knowing he refused to condemn American Nazis and the KKK when an opportunity was gift-wrapped and thrown into his tiny hands.
Three, everyone calling Trump out is exercising their Constitutional right to do so.
Four, American Nazis and the KKK praising Trump for defending them -- because they believe he has -- is also protected by the Constitution.
And finally, you can condemn American Nazis and the KKK and still be an American. Here, watch:
*ahem*
American Nazis and the KKK are an embarrassment to the 21st century.
See? That was easy. And it mirrors a very high, and increasing, number of Americans, including GOP Senators and Representatives. They, and I, have called them out for their racist, bigoted, hateful messages that defy the purpose of a mixed, united America and its people, denouncing them for their proven words and actions, and telling them in a variety of different forms to go fuck themselves.
But we haven't called for their arrest or extermination. Calling for the extermination of a group of people is what Nazis do. And when you get into that kind of incitement, your Constitutional rights are no longer the important factor. That shit's illegal.
This whole thing could have gone very, very differently. It could have been a shameful display of the most deplorable of our nation's people living out the most shameful issues of our past, people could have been called nasty names, and that could have been the end of it. But no. An American Nazi had to murder someone to express his political belief, the dominos fell one by one, and then Trump refused to condemn a group of people united solely by racism and hatred, then still squirming, he reloaded and aimed at his other foot. At no point in this did Trump violate the Constitution. He just made it abundantly clear where his priorities lie, and that's his problem, he did it to himself, legally.