First, a large part of views like "feminism" and "social justice" are plausibly terminal values.
Disagree here. Unless your terminal values include things like "everyone believing X regardless of it's truth value" or "making everyone as equal as possible even at the cost of making everyone worse off", the SJ policy proposals don't actually promote the terminal values they claim to support. One could equally well claim that opposition to cryonics is based on terminal values.
In addition, for the descriptive components of these views, "most people hold them absorbed from general culture and can't argue for them" is not correlated with "unjustified, untrue beliefs". The same description would apply to most ordinary scientific beliefs held by non-experts.
Or for that matter religious views by non-theologian theists.
Your model of Feminism/SJ differs from mine. Most of the cluster of my-model-of-SJ-space consists of the terminal value "people should not face barriers to doing what they want to do on account of factors orthogonal to that goal" (which I endorse).
My model of SJ also includes (as a smaller component) the terminal value "no one should believe there are correlations between race/sex/gender and any other attribute or characteristic", which I don't endorse.
A long blog post explains why the author, a feminist, is not comfortable with the rationalist community despite thinking it is "super cool and interesting". It's directed specifically at Yvain, but it's probably general enough to be of some interest here.
http://apophemi.wordpress.com/2014/01/04/why-im-not-on-the-rationalist-masterlist/
I'm not sure if I can summarize this fairly but the main thrust seems to be that we are overly willing to entertain offensive/taboo/hurtful ideas and this drives off many types of people. Here's a quote:
The author perceives a link between LW type open discourse and danger to minority groups. I'm not sure whether that's true or not. Take race. Many LWers are willing to entertain ideas about the existence and possible importance of average group differences in psychological traits. So, maybe LWers are racists. But they're racists who continually obsess over optimizing their philanthropic contributions to African charities. So, maybe not racists in a dangerous way?
An overly rosy view, perhaps, and I don't want to deny the reality of the blogger's experience. Clearly, the person is intelligent and attracted to some aspects of LW discourse while turned off by other aspects.