Nobody is making the argument that the players don't have the right to kneel. I haven't seen or heard that at all. They're arguing that their boss should fire them for disrespecting millions of the people whose money pays their salaries. Like when the owner of Chick-fil-A said he thought marriage was a man plus woman type deal. Or the owner of Hobby Lobby said something to the same effect. Or someone didn't want to make a gay wedding cake. Or said something off color on Facebook. Or wanted to speak his or her political opinions at Berkeley, they wanted his book deal taken away. Now that you mention it, it appears that the Left is a tad jealous that someone is using their go-to tactic and it's working. 

Odd that a bunch of racists would idolize and buy and wear the jerseys of black players in a sport that is 70% comprised of blacks. Just a thought here, but maybe they disagree with the claims concerning the police made by groups like BLM. Maybe there are some numbers that support this.