I don't see it as disrespectful, it shows that the person wearing it wants to avoid the talking and noise of the pool room and focus on the game. It personally doesn't bother me if my opponent is wearing it.
PS. Black-Balled, aren't you in Maryland? You should come down to first break in Sterling, tonight is the handicapped weekly tournament, I think Sunday we'll have a open weekly tournament starting at 4pm. But you should definitely come down tonight.
In my opinion it should be allow at all times (leagues, gambling, tourneys, etc). As long as it doesn't affect your opponent or anyone else why not?
You need to call a referee or talk to your opponent? Then get up of the chair and get their attention.
Its ok with me because I do not want to talk to anyone when I am playing anyway. I have tried it before but the cord bothers me. Some of the guys that I know that use them are listen to Bible Scripts or self help stuff. bottom line is its ok. Now cell phones that enought to drive you crazy.
Personally I don't think that anyone should have to go out of their way to get the attention of someone wearing earphones unless the earphones are to aid a hearing impaired player. I don't want to spend time worrying about my opponent not being able to hear me if I want to call a ref. It just leads into unnecessary arguments.