Counterpoint: what about respect for another's beliefs? If you were to enter a synagogue, would you refuse to wear a yarmulke? IMO, wearing a yarmulke doesn't signify that I am a follower of the Jewish faith, but rather that I respect the traditions of those who use the facility. Of course, the best option is to simply not enter the synagogue, but sometimes things happen that put us in these strange situations.
As far as the ridiculous pledge goes, I haven't mumbled that for decades. The National Sing Along is far more difficult to avoid. Each year, I and a friend attend a "banquet" to watch the NFC Championship Game (save the brickbats for watching contrived rivalries - I get it). Of course, the broadcast starts with some retread celebrity leading the crowd in an objectively horrible rendition of the National Song.
The attendees always rise for this (side note: why? is it disrespectful to not rise whenever the National Song is being played, even if it is 1500 miles away? At the OTB, the National Song is played on simulcasts all across the country and no one rises for each of the couple of dozens of times that it is playing in the background), and I do my best to be in the bathroom, or be outside, or find something to talk about with my friend that will continue (in hushed, respectful tones of course) throught the entire rendition of the song, making it clear that I'm not paying attention, with hands in my pockets or holding a glass of soda. My little display of disrespect isn't much, but I feel that it gets the message across.
RE: Self Censorship