Read about the great oxidation event other commenters have mentioned. Biology doesn't so much care about an ideal of balance.

Our beloved natural balanced ecosystems are just an artifact of the fact that unbalanced systems change until they reach some equilibrium.

It's funny that you're using the word "deserve". Based on whose moral framework? I'm not sure current moral frameworks on Earth would be against colonizing the Universe if it was possible.

Its not even about deserving it. How are going to maintain a terraforming project or build habitable orbital platforms if we can't manage keeping our natural habitat habitable?

Maybe projects like this would distract us from stupid tribalism ?

distractions don't solve problems. "just do the projects" doesn't resolve the management issue anyway. the climate crisis is a result of our inability to coordinate mass actions on a planetary scale to avoid damaging our habitat.

Maybe it would profoundly exacerbate preexisting inequality under the guise of betterment for "all" mankind.

Someone gets to choose who lives on these outposts.

Maybe if we worked together, we could actually use robots to do a lot of the initital work, then head over for fun when it's getting nice?

Once can dream I guess...

We are the only known intelligent life the universe has ever produced. Anti-natal ecoism is a bit of a fallacy.

Not the argument. The elimination of life on earth can happen due to non human causes. An impact of the sort that created the moon would do the job.