Multiple people sharing similar delusions doesn't make them basically real. Things that dont exist do not, actually, for any contrived dance around it one can make, exist.
How some illusion impacts peoples perception is relevant if you want to change peoples perception or get them to do something. It should have nothing to do with what you yourself actually think. Whatever happens to be convenient to achieving whatever goal you've decided on doesnt affect what's real.
Defining your beliefs about what you feel is good and should happen/bad and shouldnt based on whats pragmatic towards what you /already/ think is is circular and retarded.