not the best day for the "no problem" argument
I'd guess the argument is that our current artificial warming will be quickly reversed by some natural process, as seen by past cycles, even though at those times CO2 appears to be a feedback rather than a forcing.
Turns out it doesn't always work that way:
http://www.nytimes.com/2006/05/31/science/earth/31cnd-climate.html?hp&ex=1149134400&en=905c5c6d5165a0fd&ei=5094&partner=homepage
Anyway, a quick reversal on a geologic time scale would do little to limit the damage to humanity or the environment. A few decades of abnormal warmth will screw us up royally.