Respectfully VERITE, Mr.Trump like all including myself are more than free to verbalize criticism of the kneelers, boycott the NLF, call the kneelers unpatriotic, or that they should be fired, etc., whether people agree or not with his words, the president and all the American people are free to state their opinion just as you and others are free to reject it. 
What Mr. Trump is not free to do is have a bunch of goons go in a beat them down physically like Henry Ford did union organizers and protestors, or that foul man I won't mention by name who employed the Pinkerton's to open fire on factory protestors. 
I don't watch the NFL, I openly criticize their protest which I see as disrespectful to our nation, it service men and women who carry our nation's flag unto the field to be disrespected, especially in a sport owned by billionaires and played by millionaires, ones richly blessed in America.
Does this help? I appreciate your reply respectfully VERITE, you have a wonderful evening!