"It would be both total servitude and total freedom."
Paraphrasing Orwell is not a good sign
Science research: going just fine with robots. In fact, we could send thousands of more robots for the cost of one manned mission. Can a single person do more research than a thousand robots? No.
preservation of our species: absolutely irrelevant. There is no plausible scenario where Mars would be more habitable than Earth.
joy of exploration: just a fancy term for tourism
financial gain: additional examples needed.
engineering: engineering is a means to an end, not an end unto itself.
military dominance: huh?
the list goes on and on: no it really doesn't
As for survival as a species goes: there is no plausible scenario, including asteroid impact, where Mars would be more habitable than Earth. Even when Earth was hit by an extinction level asteroid, 25% of species managed to survive. That's without any benefit of preparation or technological adaptation. Pretty good odds compared to the exactly zero species that thrive on Mars.
If people want to go to Mars and can do so on their own dime, then more power to you. But Musk's total wealth is only a fraction of NASA's annual budget. So there is due skepticism that all of his public announcements are just a preamble to asking for taxpayer funding.
If you can't make your libertarian fantasy plan work out on an sub-antarctic island, then its certainly doomed to fail on Mars.
To program is to be.