It's ok, we can attack their weak point for massive damage.

Well, if the Medieval Warm Period was global, wouldn't that put some doubt on their argument that this heating is unprecedented?

Also, during the time of the Dinosaurs, the C02 concentrations were much much higher then they are now, there was no ice at either pole and the Earth got along just fine. The oceans weren't so acidified that shellfish couldn't exist. But now, with our C02 levels a 10th of what those were, somehow its going to spell disaster for everything we know?

That's a myth actually. You can't use IR to see anything you can't see with vis (the only difference is that your body glows in the IR, not in the vis, so if you're in a dark room you can see someone with an IR camera, but only if you could have seen them normally if there was enough light) IR can't penetrate walls or even stuff like glass. To take an IR spectra of a chemical (I'm a chemist) you have to put it in a salt container because IR doesn't go through lab glassware.

It's not deeply depressing because humans, as they exist currently, could not achieve world peace right now. The fact is, violence is deeply inbred into the human creature. Without a massive DNA overhaul, no human society could achieve world peace any more then a dog could achieve a deep understanding of quantum physics. It's not physically possible. Of course world peace is possible in a theoretical sense; there is no fundamental physical law requiring violence. But its not going to be done by humans, at least not in our current physical form.