Right because it would be much easier to find another habitable planet or achieve the technological ability to terraform another planet than it would be to take care of the one we have and the people we have. Yeah let's just go all in on colonizing Mars instead of taking care of things right here on earth. That seems realistic and responsible.
Discussion
It's not about what if we make this planet uninhabitable. There are lots of possible extinction level events which are not our doing. Humanity need more planets because of them.
I think we have already survived extinction level events. I'm on team human and team earth. I don't want to waste resources to achieve a theoretical reality when we have proven resources right here.
For example, which one?
Do we have somethink which can protect earth from interstet asteroid like ʻOumuamua?