Pretty sure that I saw the point made. To be fair about it, though, I don't actually care enough about either the article or Spencer to investigate it further, so I could easily be confusing it with some similar case a little. On a quick peek back, though, it was also claimed that the article itself was a pointed bit of parody, though, which was very soon followed by an article by the same author, using practically the same arguments for white people with the same conclusion.
That he's a white supremacist is a quite defensible position, yes. Possibly being in favor of forced sterilization could arguably be considered to be in favor of genocide, but that line looks like something that the author of the Salon article made up. It actually clashes a bit with the quoted bit right before it, after all.
...Giving the example of a border that was simply redrawn, by the look of it. Nothing even remotely genocidal about that, really.