I guess it comes down to how you view the concept of "the medium is the message". Should the tone be set by the creator of the software / writer of the blog post / etc, or should the end user choose one typeface for everything (or have fine-grained control over everything they read and view?)

I don't think this makes much sense as an argument, because you can have it either way with the status quo. The question isn't whether creators can use typesetting expressively; they clearly can, with a degree of freedom and optionality that would have blown me away when I started font nerding back in the 1990s. The question is whether I should sympathize with designers who are irritated by the licensing terms for Gotham or Brandon Grotesque (or whomever is doing per-impression licensing these days). I do not, and I think I'm on solid ground.