I don't think anyone is claiming that PZ Myers is representative of left wing politics, just that he is trying to make the atheism movement an offshoot of left wing politics. Which of course it is not.
Well... where is that written, though?
This is not a new schism. One (not the only) reason Mike Shermer split off CSICOP and spun his own organization was that he strongly objected to CFI's left-wing-ish message, which they felt was the logical conclusion of adopting a Secular Humanist ethic. CSICOP, CSH, and CFI were all completely controlled by Paul Kurtz at the time.
Basically Shermer's preference for Welfare Capitalism vs Kurtz' perference for Market Socialism.
That was 20 years ago, and my feeling is that over time this particular source of friction between CSI and Skeptics Society has become gradeually less important over time as the skeptical societies diluted their mandates.
To put this another way: the question of whether skepticism should be a vehicle for any particular social/political/economic 'movement' is the age-old question of: "what, exactly, is skepticism?" - Shermer believed skepticism included advocating for free market solutions. Reasoning: because skepticism is critical thinking, and you can apply critical thinking to any topic, and the free market is the best solution per critical thinking, so all (true) skeptics must be coming to the same conclusion and therefore skepticism is just as much about free market advocacy as it is about vaccination advocacy.
My local Vancouver Skeptics group believes it's marching in the Pride Parade to support gay rights.
Paul Kurtz felt it included a mandate to support abortion rights.
There was a time when atheism advocacy was tied at the hip to Communism.
Daniel Loxton thinks none of the above are appropriate for skepticism.
This relates to my earlier statements about recruiting inertia - people of all walks of life are drawn into skepticism (which is great) but they often have formed an early view based on the slice of skepticism that first engaged them. For example, if you were brought into skepticism through watching Penn & Teller's ********! it would be a shock to later learn about the modern movement's origin in the left wing politics of its founder Paul Kurtz. They may not be really aware that Shermer, P&T, Stephen Milloy, and others have been regarded as 'pushing a right-wing / libertarian agenda' within skepticism over the last 20+ years (because they view those worldviews as self evidently true facts obtained through critical thinking, rather than ordinary value laden political opinions)