Not enough time to do anything other than a link, here, and an extract:
First, I deeply, deeply regret the completely unnecessary polarization that publication of the letter by Paola Manduca caused, irrespective of our intentions, which I am very happy to discuss. This outcome was definitely not my intention.
Second, and contrary to some incomplete accounts of a conversation with a journalist I had recently, I was personally horrified at the offensive video that was forwarded by two of the authors of that letter. The world-view expressed in that video is abhorrent and must be condemned and I condemn it.
That’s not a retraction. That’s a political twist.
Further developments awaited.