The social contract says we all agree to not kill each other. If party A's fundamental stance is that it is ok to kill X group AND THIS IS TOLERATED then the social contract has been broken and party A has subjected themselves to the same rules they now apply to others.
This is not opinion. This is how it plays out in real life. If your stance is that my life is forefeight or disposable, then so is yours.
Just remember party A made this choice not their victims who choose to fight back.
This is why fascists insist there is no Holocaust. Because if they admitted it they would admit it's fair game on anyone who shares their ideology.
I can't tell if this is simply saying that you have the right to self-defense, which is obvious and agreed upon pretty much everywhere in the US, or whether it's saying that, since we've all agreed not to kill each other if those guys want to murder us then we have the right to murder them. If it's the later then either you don't understand irony or you don't really care about the 'social contract'.
It sometimes feels like folks on this community are looking forward to a cultural civil war just as much as the right-wing maga nuts.