I'm not sure about in the usa but in Australia part of being able to claim a trade mark is yours is proving you have defended it and that it's only associated with your use. So while the tribute act's use is harmless to a huge act like BJ, it may be that he pretty much needs to be able to say he stoped it, otherwise in the future a major act could steal their logo design and use as a defence "it's part of general popular culture, and been used by other bands before".

Don't get me wrong, in this instance it really sucks for fans, and for the tribute act who are clearly also fans, i'm just saying legally, it's a brand name and logo, and they have to do certain things to protect themselves in business.