Is This Pro- Or Anti-Feminist?

I've been following an ongoing discussion at Alas (a blog) regarding the potential implementation of women-0nly space/threads/forums, apparently driven by the difficulty in conducting a conversation amidst many aggressively anti-feminist posters. The idea seems to be that conversation will be more productive absent the background noise and atmosphere of intimidation. I bought that argument for the most part, and found myself wondering how exactly the content of the conversation would change in such a situation. In that sense I'm a little disappointed that they eventually decided to go for a less-restrictive policy of limiting some thread to "feminist, pro-feminist and feminist-friendly" posters only. Shortly thereafter this exchange was posted; good stuff and well-reasoned. But if you scroll down to Heart's response you eventually get to this:

The first oppression - oppression of women because we are women - occurred wherever women were assigned the tasks of sexual servicing men, reproduction for the benefit of the tribe or people group, and wherever women were assigned the tasks of the care of infants and children for the benefit of the tribe or people group. This goes back to the very earliest civilizations in all and every part of the world, without respect to race, ethnicity, religion, people group.

I've some concerns about the use of the word "assigned", since it implies choice and deliberate action. Acknowleging up front that I'm speculating at this point, it seems reasonable that if you go back early enough (Hobbes' infamous "State of Nature" or thereabouts) you get to a point where women engaged in the behaviors mentioned above by default, not through any active act of oppression. In this earliest period could anyone besides a woman have looked after the children? Men can look after infants in the modern era thanks, in part, to innovations in infant nutrition such as formula. But being unable to produce breastmilk would have disqualified a primitive man from childcare. I believe a similar argument holds regarding assignment for reproduction and possibly for assignment for sex. The ability to deliberately assign a reproductive role to women requires an understanding of reproductive cause-and-effect which was probably beyond that possessed by primitive humans; I suspect in this earliest period reproduction "just happened". During this period women could have been assigned for sex, since that's an easy enough concept for even a hypothetical primitive human to grasp, or they could have engaged in relations with men willingly; there doesn't seem to be a way to settle that question definitively. I would propose that, at least in two of the three cases mentioned above, womens' place was established by the ossification of what was originally merely expedient. The end result is largely the same, but the mechanism is different. Getting back to the original point, however, after stringing the above ideas together I was struck by the thought that I couldn't tell if this critique would be acceptable in a pro-feminist etc. thread. I think the critique itself is well-reasoned (otherwise why would I toss it out there?) but implicit in the critique are two potentially offensive ideas:

• The oppression of women could be the result of a lack of collective action on the part of womenkind at some point in the distant past, allowing then-reasonable activities to become entrenched so that they could not be altered when they were no longer reasonable.
• The oppression of women might not be the result of an active decision on the part of the male half of the species, in which case the idea that women were originally oppressed by men specifically because they were women (e.g. other) breaks down.

N.B. that none of this is to be taken to deny the reality of oppression as it stands today. But it does highlight a problem with limiting discourse on a subject to a particular set of individuals. I suspect that most pro-feminists would not object to the above, but that it might be seen as heresy by some as well. I'd like to see the folks at Alas and elsewhere tackle the problem of how to handle intra-community critiques in a limited thread. I find myself in favor of judicious banning, since a polite adversary would not appear to detract from the discussion.