Dial 1-800-FRUITCAKE to reach this guy.
What he is saying is that if you compute the temperature where the blackbody emission spectra would peak at a wavelength of 15 microns (one of the absorption bands of CO2), that temperature would be approximately 200 K (or -73 C). He then says that there would be no way to heat something that was 100 K warmer using that radiation because heat would have to flow from a cold body to a warmer body, violating the laws of thermodynamics. In short, he's delusional and ignorant, and those are his good points.
There is plenty of blackbody radiant energy available at 15 microns for temperatures warmer than 200 K, the Wien curve is very broad, especially towards the tail at longer wavelengths (I consider this the 'tail' because the photons at longer wavelengths have lower energy per photon). You don't have to postulate that the emission spectra peaks at 15 microns for there to be a significant fraction of energy available at 15 microns. (Ok, I've written clearer sentences, the point is that the emission spectra of the longwave radiation outgoing from the Earth peaks at shorter wavelengths, but there is still a lot of radiant energy flux at 15 microns for CO2 to absorb.)
CO2 does not close the atmospheric longwave window. It sits at one edge, absorbing some of the outgoing longwave flux and re-radiating some fraction of that back to Earth. If you integrate that process upwards through the atmosphere then net radiative forcing is around 1.5 W/m^2. That is huge in terms of affecting climate, solar variations are perhaps a tenth of that number, and lots of people who don't understand the physics of climate are quick to point out the huge effect solar variations have on climate.
In short, the physics of climate are known and there just aren't huge holes in the understanding at this point. It would be great if we weren't affecting climate by releasing radiatively important trace gases into the atmosphere, but we are. Nutbars and whackjobs like Nettesheim and Thune are not visionaries tied into the Truth. They are mainly people who enjoy their 15 minutes of contrarian fame or can't admit they misunderstood the theory of radiative transfer through atmospheres when they were young 40 years ago.
google "radiative transfer atmosphere" "wein blackbody radiation" other search terms. This information is readily available online or in basic atmospheric science textbooks