"Don't criticize what you can't understand..."
Black holes should not even exist, they are things with zero volume. So, basically, we have blackholes everywhere. But there you are, if it weren't for a black hole, I would not have been typing this.I think there have been plenty of responses here but basically, black holes are generally thought to exist at the core of galaxies. Black holes are much smaller than the universe and though theoretically, a universe can be so small as to fit on a pinhead, I don't believe this to be what you're proposing. I believe you are confusing dark matter with black holes. There is no absolute proof as yet that dark matter exists though a recent paper proposed the existence of dark matter stars.