I have made reference to it a few times in my public announcements, most recently
http://journals.democraticunderground.com/Skinner/380">here. I'll re-post the relevant excerpt here:
We've been much more aggressive and decisive in our efforts to identify disruptive people in the community, and (if necessary) to remove them so they will no longer poison the atmosphere for everyone else. Gone are the days when we gave problem people multiple warnings and second, third, and fourth chances that only served to delay the inevitable. We know that people don't like seeing DUers banned, especially DUers who have been here for a long time. But we have decided that we can no longer afford to let disruptive friends stick around forever, as they have made it impossible for everyone else to participate in a good-faith way. If we have to make DU smaller in order to make DU friendlier, so be it.
I'm sure I'll mention it many more times in my public announcements.
As for inoculating DU "against accusations of ideological bias/purging," I'll have to admit that this is a fairly low priority for me. I have faith that fair-minded people know that we are fair. As for the dwindling number of DUers with a chip on their shoulder and/or an axe to grind -- I'm done wasting my time trying to convince them of my good faith.