I agree in theory, but (in my opinion) the difference is that we now realize how much we screwed things up in other places, so we don't want more people to do it. It's a flawed argument, seeing as modern civilization isn't really doing everything it can to prevent climate change, so the obvious, easy answer is to not let underdeveloped civilizations follow in our footsteps.

Again, I don't disagree with your reasoning, and it is easy to back up by saying everyone else has done it, why would we stop them from doing it. I guess my argument against this point is that every society in the world should be doing their best to try to prevent things like this, so we shouldn't just let people do obviously terrible things to the environment, just because we have previously done it.

This is obviously a high-level response, not getting into particulars, but I hope you get the point at least.