If wearing them helps your game, I can respect that. When wearing them causes you tune out matters (either willfully or inadvertently) that you should be paying attention to in tournament play (stepping in front of others lies, not watching out for an errant disc headed for your dome, having to be yelled at three times to get your score) that's being discourteous to your card mates, whether they're new people or not.I get this a little, but I'm not playing in a tournament to play with new people, I'm playing a tournament to score the best I can and headphones help that. Don't really care what people perceive that as.
People who can't help but do the latter would do the rest of us a favor by not playing tournaments. Same goes for smartphones.