Well, perhaps, but don't judge from the reactions that you read on those threads that you reference. There will always be a reactionary, Luddite crowd here on FR, whining about the government doing anything -- they are not now, nor have they ever, been a substantive voice in American politics.
However, you are correct in identifying the fundamental problem -- the "lack of vision." The basic reason we have a mediocre space program is that we have no national leadership on it. This is not new -- this has been the fundamental problem for the last 30 years. After Apollo, there was no longer a perceived political need for the space program. Hence, thirty years of neglect, leading to thirty years of space mediocrity.
The problem with manned Mars missions is not the technical difficulty (although I am less sanguine than you are regarding their feasibility -- there are several things we cannot yet do at reasonably low risk levels); it's the lack of a compelling political rationale. With no Cold War and no motivation to "race" anybody to Mars, there's simply no political reason to go there. Hence, small-scale, robotic missions, of limited capability and limited return, as far as the eye can see.
The basic difference with a manned moon mission is that there is a commodity there with value beyond science or exploration (although we get that with a lunar return as well) -- the resources of the moon. The water/hydrogen at the lunar poles can allow us to access Earth-moon space routinely. Thus, a lunar return creates space-faring infrastructure (as opposed to a "one-off" Mars mission system of hardware), a space transport system that can access other places in Earth-moon space, including those involving national security (our strategic assets in orbit) and the national economic infrastructure (commercial satellites of various kinds).
Mars offers none of this -- it is basically a scientific/exploratory expedition. That's fine, but what's the political motivation for policy makers to commit to it? In contrast, they may well commit to a program that promotes important national interests (e.g., project American power in space and create new wealth by expanding access to commercial assets in Earth orbit). A return to the moon to mine water can do all this -- and create the infrastructure to go to the planets later.
That's true. Mars offers no economic benefit in itself. However, it is a high-visibility target, and--this might be important--it is possible to found a settlement on Mars. The first Mars settlers will probably not be groups of gov't scientists, but religious utopias. Just a thought.
Right, merely flying there being one of the riskiest. The radiation experienced by the Apollo astronauts was manageable; the radiation experienced by interplanetary astronauts over a space of several years is quite another thing. I have seen suggestions involving developing an artificial Van Allen belt around the spacecraft but this isn't a developed technology yet.
It isn't an insuperable engineering problem, but it's a significant one. The best place to study this sort of thing would be a moonbase, IMHO, which I would love to see set up on the same basis that Spacelab (remember Spacelab?) was decades ago. From there we can launch 'em.
Plus, I'm a real big thinker, and I'm thinking about not only colonizing Mars but terraforming it as well. Now, I know that technology is still well beyond our reach, but it is very much possible. I read an absolutely fascinating article about that possibility in Life many years ago, and the concept of Martian terraforming has fascinated me ever since. I think too many people envision any and all exploration/colonization in space as a spacesuit-only affair, but if you show them the BIG picture (i.e. starting up an actual second Earth), and actually strive to meet that goal (meaning actual research put toward practical application) then maybe, just maybe, more people will jump on board.