Ok, let’s stay within the confines of individual self-preservation.
If it is necessary for you to have a new organ to survive, but not enough are available through organ donation programs, does the fact that it is necessary to your survival mean that acquiring an organ from an unwilling donor (directly or though black market proxy) is a justified action?
How about a murderer that killed someone and left witnesses? If they are caught, it would mean they are sentenced to death. So it is necessary for their continued self-preservation to minimize the chances of being caught. Does that make their murder of the witnesses of their earlier crime justified?
Your pithy take on necessity = justification is BS at even a cursory examination.
I’m not saying that we shouldn’t have freed the slaves. Just that neither the Union nor the Confederate killing of each other was justified. I’m not saying that the US shouldn’t have fought in WW2. Just that bombing Hiroshima wasn’t justified.
You are the one conflating necessity with justification. And as such you seem to not be able to wrap your head around that while I’m saying mass violence is never justified, that doesn’t mean I’m saying the relative necessity for admirable goals means it was in the best interest of the US to have had a show of overwhelming force at the end of the WW2 conflict in mind of Stalin’s USSR post-war or that Sherman was wise to burn crops as he marched through the South to reduce supplies for Confederate opposition.
Edit: Also, thank you for making my point about how the notion of justified violence is a slippery slope that can easily end up justifying atrocities by relativist moralizing there with the whole “by any means necessary.”