I don't think people really understand the tyranny of the rocket equation and the propellant mass fraction. For the space shuttle, about 80% of the mass was fuel. Propellant mass fractions are typically around 0.8 to 0.9.
https://en.wikipedia.org/wiki/Propellant_mass_fraction
Going to Mars with people implies we're going to bring those people back. We've never launched something off of Mars before, and getting up to escape velocity on another planet (more than 2x the gravity of the Moon) isn't an easy task. The slower you go on the return trip also means you need more consumables (air, food, water) for the travelers. Not only do you have the mass to go up, but you have to land with that mass in order to launch again from the surface.
I think the future is automated settlements. A group of robots 3d printing and producing things automatically (things like methane fuel, simple parts, what if we could build a rover on Mars) would be a huge boon and start bootstrapping Mars for human settlement. We would need to take a huge amount of stuff to start doing anything interesting on Mars. Something that would take lots of trips, before we could support just a few people. People are generally quite fragile and more of a liability: limited life span, unable to easily repair, get sick or ill, bored or depressed easily...
Also, Elon's take on this three years ago:
So, to answer your question I don't think it's the case that it's similar to celebrities talking about moral and political issues in any way. I assume that he's pretty well informed but just has a totally different view that's less forward-thinking than others of his astronaut brethren.
And that may be besides the point: It seem to me this astronaut didn't make make a cogent argument from the perspective of cost-benefit tradeoffs and risk of human lives. Instead he raised vague criticisms: "It's ridiculous" and "what's the imperative... I don't think the public is that interested"
In fact available data directly refutes this astronaut's view: at least one survey from a few years ago found widespread support (about 75%) for a manned mission [0]. As of this year interest has declined somewhat [1], but still 63% rate mars as important or higher.
[0] https://www.usnews.com/news/articles/2013/02/11/poll-america...
[1] https://www.fastcompany.com/40581121/survey-most-americans-s...
My assumption is that these habitable zones would be required to generate the necessities of life in an environment devoid of any of them. Nutrients, oxygen, water... we could make recycling them very efficient, but there's always some loss. And even if you had zero loss, that's insufficient. If you're going to make a habitable zone that can support new population, you need to operate at a surplus.
The other option if you can't manufacture these resources from nothing is to import them. But that's extremely expensive. That's not a problem if the recipient is generating something of roughly equivalent value, such as mining valuable resources that can be shipped back (classic colonialism), or conducting important research (as in the case of the ISS), but if the recipient isn't generating anything of value besides somewhere to run later, then it never really gets there because it relies entirely on receiving continued shipment from the motherland.
I'm happy to be set straight on any of the above points, but these are the doubts that come to mind whenever someone argues the moon or Mars have potential as off-planet habitable zones.
Mars is not "devoid" of these things. It requires some energy to get them into usable form, but all of the basic chemical elements needed for life are there on Mars. Similar remarks apply to many other planets and similar objects (like satellites of the gas giants).
I think it's hubris to think we'd even get close to getting that correct.