First of all this issue has very little to do with the First Amendment or rights generally. This is a (mostly) private business, although the antitrust exemption makes this slightly more interesting.
I always thought Kaep's method of protest was counterproductive, narcissistic, and fairly asinine.
But then Trump came along and out-Kaep'd him by needlessly drawing attention to the issue and elevating Kaep to the status of cultural warrior that he always has wanted to achieve. Talk about counterproductive, narcissistic and asinine - but that's "our" president for ya.
Again, this is not about rights. Kaep has the "right" to kneel and the owners have the right to fire him for it. Trump has the "right" to say moronic things that further degrade his own standing and legitimacy. They both have the right to be idiots, and that's what's going on here.
Side note: I find it amusing that the folks who get offended by people kneeling during the anthem are many of the same folks who love to use the term "snowflake." If you're offended by someone disrespecting an idea you care about, your beliefs are pretty soft and vulnerable.
EDIT: meanwhile, I don't see the Bills scoring a TD tomorrow unless it's by the defense or STs. Not because of this - because their GM and coach don't believe skill or speed is needed on offense.