There are myriad ASP.NET based websites that rank well. Look at the markup on Guthrie's or Hanselman's blog. Both have WebForms artifacts like ViewState, __doPostBack, and generated IDs, but rank well.

WebForms definitely encourages sloppy markup, which I'm no fan of, but that clearly isn't the only issue Justin's having.

I think he meant the content of the blog, not the technologies used to run the blog. Still, it's utter nonsense.