It probably has something to do with the on-going saga of his relationship with the "Sad Puppies" crowd, though I think the Sad Puppies didn't actually form unt

It probably has something to do with the on-going saga of his relationship with the "Sad Puppies" crowd, though I think the Sad Puppies didn't actually form until years later. And yeah, I wouldn't be surprised if it were an oblique response to something someone tweeted at him. Getting more specific than that would probably require doing some Twitter archaeology, and I doubt that would be a particularly edifying enterprise. As entertainment options go, watching Scalzi get into minor spats with people who don't like leftist SF/F figures is right up there with reading YouTube comments.