To be fair, a lot of notable thinkers have supported the idea of colonizing other planets. Otherwise, we would be subject to extinction from one event (e.g. asteroid impact). But the recent work of researchers have ruled-out the idea of colonizing Mars. It's not technology, it's physiology. I'd have to spend some time to dig it out, but the summary is that any people we sent to Mars would probably be ill by the time they got there due to renal problems/failure. And a round-trip would be out of the question (they'd be dying or dead by the time they got back for the same issue).

Musk may not be aware of this issue.

I do agree with your point about preserving the one planet in the universe that a) we know can sustain us, and b) we're already here.