Ofcourse black holes exist! What do you think is projecting our holographic galaxy if not the black hole? The mass of a black hole is directly proportional to the size of the galaxy ie the projector is a big as it needs to be for the size of the projection.
Projections need a screen and the dark matter which surrounds and protects our galaxy is the delimiter. So you have no need to worry about the nasty rumours of Andromeda crashing into us.
You might wonder what my source is? I pulled it right out of my ass.