Mars would be an appalling place to live, even if were even possible (which it currently isn't).
What makes you so certain?
I think it is objectively a terrible place to live, at least from a human perspective. There maybe lifeforms adapted to -60c to 20c temperatures, almost no atmosphere, no surface water, 0.3g gravity, lashings of ionising radiation and a diet of dust. That's not us.
I contend that it's absolutely certain that we could live on Mars, for a while at least. After all, the moon is even more appalling than Mars, yet people were able to live there for a few days.
You are stretching the term "living there" somewhat. Visiting might be the proper term. I've no doubt that given the right equipment humans could survive for some time there. That's a long way from anything you could refer to as a colony, which is what I'm arguing against.
but that's all part of the pioneering spirit that lives deep inside the hearts of the select few who are willing to face the challenges to make it happen.
This sort of stuff is probably more in the cultural DNA of Americans than us Brits, so maybe we just don't get it.
However, as I said before I don't think the desire to go to mars has anything to do with say the desires of the Mayflower passengers or even from the pioneering/exploring spirit of someone like Ferdinand Magellan. It comes from the same desire there was to climb Everest, which, as George Mallory put it so honestly when asked why he was doing it, said "because it's there". Acknowledging that is ultimately pointless and irrational, but he still wants to do it. I get that.
If the likes of Musk gave that as answer I'd have a lot more respect for them. Instead egomaniacs like him have to somehow align this with saving humanity or some such drivel. I'm sure it will sell a few cars though, he's not daft.