I don’t know anything about him, but would bet that he was a marginal player, and that’s why he’s not in a big league spring training camp. Not because of him kneeling.
Same deal with Kapernick.
He’s a LH-hitting defensive catcher with marginal hitting and not great at throwing out base runners. The demand for catchers in Spring Training is such that he would have at least an invite. There’s no doubt teams don’t want his kind of trouble; anger issues combined with pissing off fans.
Have to be a star, or at least an everyday player, to overcome those issues.
If you have a choice between two players, and one is a PR liability, you pick the one who is not going to alienate fans.
MLB will keep anybody if they can hit (especially with power). Look at Daryl Strawberry and so many others that played after they had already served time. Strawberry had been arrested 17 times.