Clearly he had a good handle on the scale of the sheer resource waste of the lunar missions, and feels that if man is going to Mars it should be for a definite plan to do something quantifiable with the presence, rather than just going there, planting a flag and doing a few experiments (longer-term in the case of Mars, but still insufficient science) and coming back, and repeating it a few times like the Moon.
The lack of a magnetosphere is the biggest problem though - unlike Earth, just because you've landed on a planet doesn't mean you get any protection from the Sun. I don't believe they still have any kind of really practical, long-term answer for that one.