That's my point exactly. It doesn't matter whether the Borg are alive or not, it doesn't matter what rights they have, they're a menace that only seeks to consume and destroy. That in and of itself necessitates their destruction.
You are missing the bigger moral dilemma that Picard eventually saw regard Hugh which he himself (and Seven of Nine) embodies. Yes the Borg are a menace. But each drone disconnected from the Collective is an individual. Condemning the entirity of the Collective into oblivion means the destruction of trillion of innocent individuals as well.