I would never leave any fandom just because there are "bad" people or something... First, the "fandom" should be a lot more about the thing you enjoy/like rather than the other people who also like it. Plus, there's "bad" people everywhere, in any fandom, group, circle of people, as long as there is people, there will be people with whom you can make a connection, and others not, some good people, some not so much etc.
About Mejibray, I haven't listened too much from them, from what I've listened to, it sounded too basic and not very interesting, so I just moved over to the next bands xD but I don't "hate" them, couldn't care less. xD