you may as well kill them, because if you don't, they'll sue.

Yes, but that's not a legal argument. In fact, saying that in court as justification is a fucking terrible idea.

It may be additional rationale, but I'd imagine the best bet is to just stick to the explanation of adrenaline and self defense. Don't say you wanted to kill anyone; you wanted to defend yourself, and were (correctly) worried they were still a threat to you.

EDIT: Oh and, most importantly, don't say ANYTHING AT ALL without your lawyer present. Don't be like Alec Baldwin.