I've actually seen that kind of superiorist attitudes from all kinds of martial artists, including many in CMA/JMA/KMA. In fact, some of the worst I've seen or experienced has been from some other CMAists. It's not limited to BJJ people. Maybe it's more human nature than style-specific nature?

I trained over a year at a BJJ academy, and maybe I was lucky, but none of the people I trained with there, including the teacher, ever said anything negative about other MAs, that I ever heard. They seemed like a pretty open-minded group.