There's a lot of interesting ethical concerns about the Borg Collevtive. It's easy to think of it as some big, alien, external force that erases minds and uses the bodies as flesh puppets. But that isn't how they're described at all. The people are all still there, that big scary intelligence is made up from merging all their minds together. Obviously, the consent issue is problematic, and we know people generally find it horrific when they are freed. But the fact is, the majority of the Hivemind apparently don't mind, the hive mind is made up from the gestalt of the individuals, and that is the only thing keeping individuals from leaving.