"I think your understanding of the engineering challenges and demands presented by the launch market is deficient, and thus your undertanding of the proper role of government in it is way off. "

Care the explain your statement a bit more?

"Mars' core has pretty much cooled down, and thus it lacks a magnetic field to shield it from the Sun's deadly radiation. It will never be terra-formed, and thus Mars, while interesting, is of limited use, and always will be. Always."

Hmm. The magnetosphere is mainly significant in blocking charged particles (a type of radiation). There are two main sources of charged particles: solar flares and charged particles from other stellar objects (galactic radiation). All radiation from the sun is less at Mars distance in comparison to Earth distance. Also the Sun has a large magnetosphere which blocks "to some degree" the galactic radiation- when the sun is more active there is less galactic radiation at Earth distance (therefore it's logical to assume there is more galactic radiation at Mars distance than compared to Earth distance).
The above is in regards to the "Sun's deadly radiation". As far depleting a terraformed atmosphere the above is somewhat irrelevant.
But I'm somewhat at loss at understanding why you replying to me regarding this issue: terraforming Mars doesn't seem to me to be pressing issue- and not something I favor.

"That said, if anyone wanted to go to Mars, the cheap way to do it would not be Zubrin's Mars Direct, but rather to use solar dynamic propulsion to propel an Aldrin Cycler variant equiped with closed loop life support."

I agree with you that if you were interested in doing any major project on Mars (such as colonizing or even a modest size manned research station) the cycler has many advantages.

"In any case, it is simply irresponsible in the extreme to spend any money on manned Mars flight before an adequate defense against comet and asteroid impact is put in place."

I do (of course) agree the taking steps in order to protect the planet from impactors should be a high priority.