Environmentalism isn't an excuse to give up on every other aspiration humanity might hold.
Personally.
One needs beauty in the world, yes, but one also needs to breathe.
Anyway, what's the point of focusing all efforts on Earth if human civilization is going to die out here anyway? That's the path we're currently on, and stopping space exploration isn't going to magically fix that. Wanting other baskets for the egg of human civilization is just pragmatism.
If humanity dies or goes pre-industrial because someone engineered a supervirus and we refused to put effort into space travel, all our conservation efforts won't really matter much.