I suggest you read ATTP's post on it, and this, and the comments following.
As he says, the "lukewarmer gambit", being the last refuge of people who don't want action taken (usually for purely ideological reasons), is a still a "rejection of evidence" position, tarted up as if it's "just being reasonable here":
This is wrong on many levels. Firstly climate models don’t assume large positive feedbacks; the level of positive feedbacks is an emergent property of the models. It’s one of the things these models are trying to determine. Secondly, climate models are not the only reason why we think that feedbacks could be positive and large. Palaeoclimate estimates of climate sensitivity are also in line with estimates from climate models.As with your false equivalence attempt on the doctor who came up with his own oddball Hillary health conspiracy: stop doing that (false equivalence). The Right wing conspiracy stuff about Hillary's health has been massive, relentless (and ridiculous) and given a high profile on Fox News for many months, convincing large numbers of dimwits. They haven't been "concerned" about Hillary's health - they've been exploiting everything out of context, from a photo after a slip on stairs to a joke head movement slowed down on video with scary music to argue she has everything from dementia to Parkinson's to HIV. It has, truly, been "tinfoil hat" material. And as for the doctor and his poisoning tweet - he's only getting attention because he is famous for other high profile work, the article is brief, and I don't think the paper is doing much to suggest it should be taken seriously.
Finally, even the energy-balance models preferred by Lukewarmers do not rule out high climate sensitivity, and this seems to be the main problem; anyone who says “warming is likely to be mild” is essentially dismissing evidence that suggests otherwise. The discussion that we should be having is what we should do if climate sensitivity is high enough that our continued emission of CO2 could lead to substantial changes in temperature, the hydrological cycle, and extreme events. If one group has already decided that this is unlikely, and that we shouldn’t base policy on this possibility, what else is there to discuss?
I would argue with you on twitter, but I'm not keen on the word limits...
Update: another bit of blog commentary on the McArdle shrug shoulder attitude of "sure, I don't dismiss it could be a major problem, but it might not be too, and no one will go for a carbon tax; so what can you do?