Maybe not get up and leave but consider that if someone just didn't come back or stopped coming because of it but would not feel comfortable saying so, you might never know the reason.
Yes, every time I visit "they" do this ritual. At one time lack of flag in meeting room did not stop them , they "waved" smart phone with the flag on screen. It is still free county but I find it hypocritical to even assume it would be OK not to participate in it , especially after what is happening to the fellow who "took the knee". And yes, one of the many reasons I am "just a visitor". I find such ritual very cheap way to "publicly display patriotism", nothing else. 73 Shirley