I don't think the issue really has anything to do with the "criminal bigot" that conservatives put in the White House. Trump - who is not very wise - should have simply said, "Look, I have owned a football team, and while the players are free to do as they like, I am not sure it is good for business". And he would have been right, because they players have lots of other avenues for protest than not standing for a national anthem.
On a personal level, I don't feel any differently about what today's football athletes are doing than what Tommie Smith and John Carlos did in the Mexico City Olympics. I think they are being treated too harshly by some, because while they are well paid, they are at the same time exploited by a league which has nowhere near the contracts or protections that MLB and NBA players do, and their health is at considerably more risk than with other sports (boxing and MMA excepted). One can see where they are coming from, especially given their experiences (by and large) as black Americans. They have short, dangerous careers for the most part. But all it is a reminder that pro athletes - paid entertainers - have to pay attention to the paying public. My guess is that the current players are alienating a few, or a bit more than a few, and while I think conservatives are overstating the matter when ascribing the NFL's lower ratings and attendance to the kneeling before the anthem conduct, it still is a factor and at the end of the day likely not a wise business decision.
It all must be observed in context, too. The players by and large don't have as much of a rope with the everyday public as they used to. And it is in large part due to the players' conduct. (And I am not talking about the anthem protests).
Just yesterday, Odell Beckham was given a misconduct penalty for acting out after a touchdown. What was he doing? He was acting like he was urinating like a dog (on the Eagles team name). These kind of antics wear thin, because it give off vibes that players care more about getting on Sportscenter or fulfilling immature impulses that winning the game. And yes, the Giants lost the game! Fans like a good product, especially at the outrageous prices for tickets, parking, and so on, and that includes players who act like they have done it before. And in the past, good team members would get a guy like that to knock if off.
The antics like I describe above are turning me off to the game, and that is a hard thing to do (my grandfather played professional football in the 30's). But at some point it all gets tiresome, because what keeps fans in the seats and on TV screens is good, disciplined team football.