My Master has only said that training in two arts is not an easy thing to do and that one should get their Judo Blackbelt before doing so, which I have done. Nowhere has anyone ever told me not to train BJJ.
Cool, then if he never said anything against training in BJJ, go for it. never mind the other BB.
It is about doing the right thing towards the instructor that did bother putting a BB around your waist.
the rest of the tribe can get stuffed.