Mitigating factors aside, it is clear that anti-Semitic remarks were made in the comments section of McClellands blog, some (arguably) by McClelland himself. Since my understanding is that McLelland is to the Blogging Dippers what Cherniak is to Liblogs (roughly speaking, McLelland "owns" the site), demanding that he step down is like demanding that the stars fall from the sky. There's no point to it. I would, however, suggest to McClelland that he offer something in the line of an apology. Everyone says dumb things occasionally (or allows them to be said in one's presence), and the best thing to do is own up and move on.
And if you do feel like slagging off some ethnic or national group, pick a relatively powerless one, like the Ystonians. There aren't many around, and most of those that are look like they grew up next to Chernobyl. They're reedier than the English! So if you see any you can usually out-run them and, failing that, they can't throw much of a punch.
The thing I'd like to know is: where's that conflict buzzard Kinsella? Shouldn't he be flapping around making free with the denunciations?