Oh yes, mineshafts, I love that one, let's do that as well, sign me up. What's the required men to women ratio, again, doc?
So what you're saying is, it would be (1) more boring than ISS, and (2) quite a bit more dangerous. I'm sure both are true - discovery and exploration have always been very risky, and this would be unprecedented so I'm sure it won't be a walk in the park. I'm not sure, but I don't think it would be boring and dangerous enough to be impossible. I am sure, though, that that hasn't stopped us before.
A colony on Mars won't be self-sufficient for a very long time, even if they get their water from the planet, and produce their own oxygen and grow their vegetables and stuff. It may take a century or more, if we ever manage to have factories there, to produce parts and things they'll need. But to use your own words: "It would take infinitely long if you never start."
What I don't get is why you seem to assume that it's one thing or the other. It seems to me that you're implying that, if we send a manned mission to Mars, we won't develop better technology here. We can do both. It could be that we will solve the transport issue before we solve self-sufficiency away from Earth, or it can happen the other way around, I don't think you, me, or anyone else can predict now how it'll play out. So predicating the solution of a hard problem on solving another first, that may be less or maybe much more difficult, does seem a tad self-defeating. Especially when I don't see a hard dependency, both problems can be tackled at the same time, without waiting.
Anyroad, gotta get to work. Some quick notes I thought of while reading your post, that I have no time now to edit into a proper reply:
* You get used to email, really, and you don't need low latency to stay in touch with friends, and get movies and videogames. Or, radical notion here, books.
* It could be that very earthly jobs, like in the military or law enforcement or what you have, are riskier anyway, it's not as if we don't take risks every day (we as a species, I mean.. felt embarrassed and a bit ashamed about that "we", from the comfort of my safe living room).
* It's not about repopulating Earth, it's about survival of the species by any means necessary, even if it means evolving to live elsewhere and that we can't go back. Mars is certainly harder than Earth, it probably won't be viable, but we'll want to try other places eventually. Out there, away from the solar system. And hey, we have to start somewhere, and Mars seems easy enough. Considering.
* Good luck with PETA letting you send a couple monkeys. Mark me words, it'll be easier to send humans anyway. Heh.
* To the AC asking why should we care... that doesn't even deserve an answer. We'll get extinct one day, guaranteed, but we're going to go down fighting, because that's who we are. Humanity ftw.