Not defending killings on either side. That said, one side is already using all kinds of nasty tactics, including killings.

Environmental destruction is a problem that needs massive, urgent action. We have seen over and over that nicely asking corporations to behave doesn't work. I don't know what the solution is, but I wouldn't be surprised if fed up people take up violence. It will probably just worsen the situation.

It won’t necessarily make it normalized. But killing someone in some very special context can be morally right, I think. Euthanasia is a more common example, but I believe killing Hitler would be similarly non-controversial.

But it is an age-old question of philosophy.

https://askell.io/posts/2020/12/bad-isnt-good-enough Per this article, risking normalizing a bad thing is a pro tanto reason not to do something, but it's not an "all things considered" reason not to do something. As the sibling comment says, there are circumstances in which killing is widely considered acceptable. I think the ethical considerations here are complicated and worth serious investigation, although I do firmly come down on the side of "let's not murder people."