This is a bit bizarre. Slate and The Atlantic are already center-right publications (I know my soon-to-be-former colleagues at The Atlantic don't necessarily see it that way, but it is).
I'll refrain from commenting on my own publication's politics and just say that describing Slate as "center-right" strikes me as more than a little weird. True, Slate publishes some writers whose politics Matt would probably describe as right-of-center - from Emily Yoffe and Mickey Kaus to Christopher Hitchens and maybe Will Saletan, among others. Personally, I would describe some of these people as either center-left or - in the case of Hitchens, especially - entirely unclassifiable, but for the sake of argument let's accept Yglesias's progressive-centric premises about who's right and who's left. Even then, it's awfully hard for me to see how a publication where Fred Kaplan is the go-to guy on foreign policy, where Dahlia Lithwick and Emily Bazelon cover law and social issues, where Timothy Noah writes about domestic policy and politics, and where everyone from David Greenberg to Stephen Metcalf to Meghan O'Rourke to Amanda Schaffer to Dana Stevens can be counted to provide a center-left (or just plain left) take almost anytime they touch on politics, can be reasonably described as "center-right."
Update: While I was writing this post, Matt clarified himself a bit: "I'll admit that while I look at Slate all the time, I'm not a particularly thorough reader of it and the Mickey Kaus phenomenon looms large in my mind." I think if the Mickey Kaus phenomenon looms large in your mind, then you're probably reading Mickey Kaus way more than you read Slate. (Which is easy to do, admittedly, if you spend most of your time reading blogs ...)