Earlier quoted context omitted.
Let me recolor that question: If you had some Lex Luthor powers, and there were 4 billion people hell bent on killing you, and the only way you could stop them was to use your huge robot army and your giant space lasers as a military force against them -- would you do that? I suppose the fundamental question here is: to what extent can you exercise your actions of self interest if they mean countering similar actions…
Yeah, that's an easy one, I feel perfectly okay applying force in response to aggression against what's belongs to me (like my body). And no, the fundamental question is "why would someone think that ozone layer or forests etc belongs to them" (because if it doesn't, they are not in position to decide if it should be kept or destroyed).
Do you have the right to defend yourself against an indirect attack? Here's another ridiculous scenario to think about - let's say you're diabetic, and some group of thugs is destroying all the world's supply of insulin. It doesn't belong to you, but you definitely need it. What would you do?