Their statement was about ensuring that "Any owner of Manchester United must commit to making football a sport for everyone". That's pretty nebulous and certainly does not conclusively end at members of the LGBT community simply being allowed to exist within football, as you suggest it does.
I'm extending Rainbow Devils the courtesy of assuming they aren't thick enough to believe that Sheikh Jassim was going to ban LGBT people from the stadium, or otherwise explicitly discriminate against them, upon taking over at United. Therefore, I'm assuming there are other factors driving their decision to issue such a statement, such as the conflict that any LGBT players, staff or supporters might have in representing a club owned by representative's of the Qatari state, or the fact that Qatari state ownership of Manchester United might well legitimise their position on homosexuality in the minds of some Manchester United fans (i.e. sportswashing). Evidently, you don't wish to extend them this same courtesy, and would rather assume that they were genuinely naive enough to fear they might be banished from the stadium upon Sheikh Jassim's prospective take over of the club.