As Picard later said, "The moral thing to do was not the *right* thing to do."
As for Beverly, she didn't seem to be speaking so much in character as just essentially offering an opposing anti-genocide opinion.
After all, in BOBW she was devising a plan to use destructive nanites against the Borg, which could have decimated the collective as much as the invasive program strategy.
I think we can safely assume at this point that the Borg can shut of ships with "diseases", or virus computer infections, etc. In this case, Picard's "genocidal" plan wouldn't have worked and may have actually "pissed off" the Borg...which would have made things WORSE. So taking into consideration that there was no guarantee the plan would work, Picard did the right thing. As we saw later this had other repercussions with Hugh and Lore on an isolated ship (further reinforcing the idea the Borg can shut off individual ships from the collective), but blame Picard for the continued existence of the threat?
I don't think so.