Admiral Necheyev said it best... Picard's first duty is to safeguard the lives of Federation citizens, not 'wrestle with your conscience'. Picard himself said later in the same episode ("Descent") that the moral thing to do might not have been the right thing to do. And there IS a difference between the two things sometimes.
(As far as I'm concerned, because Picard didn't even attempt to use the weapon in "I Borg", it makes him at least partially responsible for everyone afterward who was killed or assimilated by the Borg.)
Assimilated Borg... it is tragic, and it's terrible. But completely honest? Absolutely, they must be eradicated. The Borg can't be bargained or negotiated with, and they will just keep on killing and assimilating until the entire galaxy is Borg. While this does kill billions, it will save trillions from suffering the same fate (or death... if they are lucky).
Basically, the Borg are a disease. For those who think Picard was right in not attempting to use Hugh as the carrier of the weapon, let me ask you this: is it right to allow billions and billions MORE people across who knows how many races to either be killed or assimilated by not even attempting to end the Borg?