I'd just like to throw out there that Edit_XYZ was moralising killing all the Borg in terms of self defence/necessity...
I've said before and I'll say again I'm not too hot on US Law, I watch Boston Legal but that's where my knowledge begins and ends, so what I'm about to say speaks to English Law:
Necessity is never a defence to murder, never. If someone puts a gun to your head and tells you to kill a third person or you will die, English Law expects that you will do the right and proper thing and refuse to do so even if this means that you will die - nothing will ever give you the right to decide your life is more important than an innocent person.
In english law - perhaps not.
In
most law systems known to man (not only US law, but US, most european, etc) - state of necessity most definitely IS an exculpation for your act, if certain conditions are met:
-the harm you'll cause by acting is smaller than the harm that will come to pass if you won't act;
-you had no reasonable alternative to your action - 'reasonable' alternative as in, you, a normal person, can discover it + the chance of this alternative 'working' are not minimal.
If these conditions are met, in most law systems you have the right to defend your life (or the life of another) against a person who cannot control his actions and is about to kill you - even by killing said person, if no other options are available.
You are saying that, in english law, you are legally obligated to essentially commit suicide in such a case? Creepy.
In the case from 'I, borg':
- the borg are currently engaged in a campaign to assimilate the entire galaxy - MILLIONS of civilisations - killing TRILLIONS of conscious beings. Yes, TRILLIONS - an atrocity on such a scale that human minds can only understand it as a mathematical abstraction.
The harm done by Picard&co when unleashing the paradox virus is far smaller than what the borg were doing and had in mind for the galaxy (and that is assuming the paradox virus would actually KILL the drones - which was not established in the episode).
-Picard&co had no other alternatives with a reasonable chance of stopping the borg.
'We'll win the lottery tomorrow and the borg will be destroyed by a godlike species' does NOT count as an reasonable alternative - with a reasonable chance of success.
And that's what we're talking about with the Borg, killing innocent people. It is the consciousness which is causing the borg to assimilate. Not the Drones. Picard's solution is akin to destroying every terminal that can access the internet in the world, because then we will destroy computer viruses...
AKA - with respect to the borg drones - Picard would be in a state of necessity when unleashing the paradox virus, even if the drones would be killed by it - and this is a BIG IF.*
*You see, 'I, borg' never established whether the drones would die.
During the episode, Picard choose not to dismantle the collective consciousness (destroying a 'culture') because he would have to use Hugh to do it, and using a person is 'bad'.
All the future victims of the borg and the fate of the borg drones were never even mentioned.
Why?
Because, as in 'endgame', the scenarists simply didn't think things through.
And as for self defence, in order to suceed in self defence you have to be able to show that you believed that there was an immediate threat and that in those circumstances your actions were justified...
You are in self-defense if you act to protect your life OR THE LIFE OF ANOTHER.
In 'I, borg', it was crystal clear - to everyone, but especially to Picard - that the borg were engaged in a genocidal campaign against, virtually, all other conscious beings in the galaxy - killing BILLIONS upon BILLIONS on an ongoing basis (let me guess, JB2005 - that's not 'immediate threat' enough for you

).
With regard to the borg - acting to stop this continuing megacrime is self-defence, regardless of whether the borg target you during this specific second or not.
genocide can never be a justifiable defence. Never. If you're telling me that the Federation's policy is "it is better that you all die so that we might live" then I want the Borg to win...at least there's no malice in what they're doing...the Borg are the embodiment of the phrase "we're from the government and we're here to help you" and nothing more, there is no evil in what they do...
In 'I, borg', genocide was upon Picard, regardless of his choice:
He chose to allow the borg to continue killing and assimilating across the galaxy - becoming partly responsible for the death of BILLIONS, entire civilisations, because he could stop all this horror and didn't.
A lot of blood stains Picard's hands - inheritance from 'I, borg'.
And there's no malice on the part of a person that acts in self-defence or state of necessity. If you actually beleive there is, you don't really understand the concepts of self-defence or state of nesessity.
On the other hand, on the part of the borg, a
conscious intelligence (as was repeatedly established), there most definitely is malice.
Consciousness = amenable to moral judgment.
The borg is no mere automata, no mere unconscious killer asteroid or PC.