He's talking about cutting off the link juice FROM sites TO blackhatters' sites, right? But then he mentions blackhat forums, and that's where the confusion is - makes it sound as if they're going to tag everyone at these forums, locate their sites, locate their inbounds, and choke the PR out of those inbounds. Which I don't think is what he meant.
One thing I am wondering about is: a lot of black hatters get their inbounds NOT from their own link schemes, but through hacking innocent sites and/or leaving comments on blogs run by people who don't realize "Your site most venerable ever, I add you to Facebook" isn't a real comment. So maybe that's what he's talking about - finding a way to automatically neutralize such "upstream" links without penalizing the sites that unwittingly provided them?