Permit me to offer a few thoughts in an effort to turn this thread to something related to our site and away from politics:
I served in the military for 30 years, so I think my patriotism cred is solid enough to withstand whatever hits I take from saying I'm not fond of coerced public demonstrations of loyalty.
Thus, I think the team's official position is correct. They encourage but don't require participation. Players may be citizens of other countries. They may have urgent pre-game matters to tend to. They simply may not want to participate. The team gives them the choice. That seems reasonable to me.
However, players who choose not to participate should do so in a manner that doesn't distract from the business at hand, which is playing together as a team to win a game.
Many players feel strongly about all sorts of political or religious issues. Presumably, they don't all agree. Calling attention to one's individual opinions moments before game time when teammates are in the final stages of their pre-game preparation is not likely to have a positive effect on the team's focus, motivation, unity, and performance. This makes the demonstration selfish.
In addition to being selfish, it's bad manners. The playing field, sidelines and dugouts at sporting events are not forums for players to express opinions on subjects unrelated to why they are on the field. The team owners invest a lot of money creating the game day stadium experience for the fans, and it is rude to hijack that experience for one's own purposes. (Also, that carefully scripted game day experience is designed to keep people buying tickets so the teams can pay the players.)
Part of growing up is learning that the world doesn't revolve around you and most people really don't want to know what you think about everything. I recently went to a religious service of a group of which I am not a member. I didn't care for it and disagreed with much of it. I suppose I could have made my disagreement known by refusing to stand or kneel at the designated times and by holding a news conference in the lobby to explain why. But I didn't. Nobody asked my opinion, so I kept it to myself and smiled politely. Would that have been too much to ask of this player?