"In this nation anyone and everyone has the right to make their views known at any time." 
"Their critics and sponsors who dropped the players for their pro-America activity of free speech are the real un-Americans."

Do you seriously not see the discrepancy in those 2 statements, you with your A in Constitutional law?  Owners, sponsors, and the critic in the stadium seat or in front of the TV have the same right as the players to express their views, even negative, about those players. If their opinion is that the players are behaving in an unprofessional or un-American way, they have the right to state that, either directly or in hiring or purchasing decisions. 

"Un-American" is only an opinion that anyone has the right to express about someone's speech. You, the critics, anyone. The values and principles represented by the anthem, the right to  express one's views without fear of arrest, applies to critics of Kaepernick and Marshall as much as they apply to Kaepernick and Marshall.