My belief is that many people will think "Oh good! A safe harbor where we can fix our mistakes!" My problems with this: 1) Is everyone going to Mars in a reasonable time frame, or are people going to be left behind? Permanently? 2) Are we actually going to fix the Earth? Let's assume many people will be there for a while longer. 3) Are we going to not wreck Mars?
#1 That is an extremely dumb thought to project on everyone else. Mars isn't an a replacement for earth, and wont support even a tiny fraction of the population in the foreseeable future. Why do you believe people will think this?
#2 I hope we fix earth, but we either will or wont completely independent of Mars policy. Again, I dont see how they are related. Is the idea to prevent Mars activity as a motivating punishment (e.g. Birthday parties are cancelled until you clean your room)?
#3 What does "wrecking Mars" mean? What is a good Mars and what is a bad Mars?
To 3, I'll vaguely say "like how we are wrecking the Earth". To 1 and 2, I think you have a far more optimistic view of the technical and social aspects of this issue than I do. Dangerously so. Enough people look at Musk and others talking about Mars, or "believe in the technological revolution", or don't care about the Earth, that fixing the issues on Earth is a very urgent matter with not enough mindshare.
waging war and trying to destroy people's hopes and dreams is a cynical, toxic, failing strategy for environmentalism.
It communicates that environmentalism cant maintain mindshare based on its own merit, and must obstruct and tear down other goals. Unfortunately, this alienates anyone one who holds values on par with environmentalism.
Reposting another of my comments to summarize my thoughts. Mainly read the last paragraph in your case. I think you are too optimistic. It may be the case that environmentalism can't organically get enough mindshare now, and we're waiting on a miracle. But I would say I have a far more balanced view of the situation, especially since mitigating negatives is "pessimistic" by nature, and it is not an agenda I push for so much as something people must either accept or deny.