It doesn't bother me at all, it's within the rules of the game, and there is a traditional understanding in baseball that players affected by rules changes are often grandfathered. It happened with Burliegh Grimes and the spitball, as well as with batting helmets, IIRC.
If every one got to wear one, fine. But you have to get an exemption to do so. Therefore, it makes it an unfair playing field. By the way, he didn't start wearing it until the 2000 season, since then he has hit 258 of his 703 home runs.