I think this is twaddle.

If by "respond to the downvoting in kind" you mean something like "start downvoting articles from the Evil Feminists even when there's nothing in the articles themselves that would have made us downvote them if they'd been written by other people", then it's that that would be the first step to a "karma cartel" situation. (And "in kind" would be just plain dishonest.)

If by "respond to the downvoting in kind" you mean something like "start downvoting articles that we think have negative net contribution to the Less Wrong community because they encourage harmful attitudes", then you should be doing that and there's nothing cartel-like about it.