They can refuse to honor the country without insulting their fans and the rest of the citizens in the process. If they don't want to put their hand over their heart and honor the country, that's their right... but sitting, kneeling, "black power" fist in the air, etc are blatant slaps in the faces of all their countrymen, their fans, who do honor this country. They should stand there politely with their hands at their sides or behind their backs, just as people do when another countries anthem is played, to show respect to the people of that country. Even Obama does that much when the anthem or the pledge takes place.
The fact that they are members of teams only compounds the problem, they not only insult all the citizens of this country, they disrespect their teams and make them (the teams) look bad as well. That soccer broad that has been kneeling is on the US team for petes sake. That's yet again another level, if she hates this country so much that she insults the citizens and disrespects her teammates, then why in the hell should she be allowed to play for the US team? She shouldn't.