star trek - Why didn't Picard go through with the "geometric pattern" plan against the borg?

In ST:TNG Season 5, episode "I, Borg", the crew comes across a damaged Borg individual that they isolate from the collective, and name him "Hugh".

They develop a plan to show an irrational geometric shape and return Hugh to the collective. Their goal was that the unsolvable shape would, over time, overwhelm their processing power and effectively 'lock up' their systems.

Toward the end of the episode, they decide to give Hugh a choice of asylum or returning to the Collective.

After Hugh chooses to return, Picard hopes that his humanization would spread to the Borg. But he portrayed it as if it was an optimistic hope at best.

Why didn't they go through with their original plan anyway? It wouldn't have changed anything for Hugh since the crew already established that they assumed that if it was discovered by the Borg that Hugh had thoughts or ideas contrary to the best intentions of the Collective, his memory would be erased.

Earlier in the episode, Picard made it clear that since they are not open to peace negotiation and only seek to annihilate the Federation, in Picard's mind any action is justified. (Which of course is somewhat contrary to other Picard lines in different episodes/movies. So this is assuming Picard's current frame of mind.)

I understand he wanted to make an exception for the recently-humanized Hugh, but shutting them all down would still accomplish his goal. He could then find Hugh again, without threat of destruction, and replace his neural processors as they suggested they could earlier in the episode, to undo any overload that the geometric pattern may have caused, and thus easily returning Hugh to a working state again.

Is there some other reason I am missing, or is this a plot hole?

Answer

Picard's change of heart hinged on his realization that Borg members retain individuality, sentience and autonomy when not submerged in the collective. He initially believed that the Borg members were functionally equivalent to organs or limbs in a human; they should be given no more regard than a severed arm or leg. If Borg members retain a separate viable existence when removed from the collective, then the rules of war apply with regard to individuals and states, and how individuals must be treated when no longer acting as combatants for that state.

Also, if Borg members retain individuality, then it becomes immoral to wage total war, i.e. commit genocide without any allowance for surrender for individuals suddenly left without a functioning government. The Borg collective as a form of government was a legitimate military target, but totally wrecking the collective with nothing in place to sustain the members suddenly cast adrift is as good as genocide. The weapon was too big; Picard realized that it was immoral to use it.