One of the reasons this post is interesting is because I don't expect it to raise any sort of debate at all - I expect pretty much everyone who posts on LW to be pro-choice. Is this because LW people are part of the "Correct Contrarian Cluster (although it isn't so contrarian in this context)"

This is nearly the opposite of 'contrarianism' (as you partially acknowledge). The 'pro-choice' stance in most cases will be more to do with conforming than coming to a Correct choice. In fact Correct barely fits either, except to the extent that it is part of my (or our) extrapolated volition.

I expect pretty much everyone who posts on LW to be pro-choice.

I am most definitely not pro-choice. Most particularly with the 'am' part (it is not part of my identity) and in secondarily with the 'pro-choice' part - abhorring involvement in that sort of weasely definition is part of my identity. (If you prefer you could say that I am pro choice and pro life and balance the competing desideratum with a complicated system of intuitions and reasoning.) But for practical purposes I'm still going to check the same box when faced with the question "Would you prefer safe and legal abortions to be available to pregnant women (and Californian governors) at their own discretion?"