To be sure, there is a lot of self-censorship -- the Overton window is real, and it's not advisable to say things fully outside the Overton window. Perhaps Altman is saying that the Overton window is closing on some opinions that he thinks we should be able to discuss openly, but because they're now outside the window he feels unsafe mentioning them. That would be a fair argument, though it'd be nice to make a list of things that can and cannot be said publicly, then we could argue whether we should widen the Overton window.

I happen think the Overton window is a good thing, even if I'm not always happy as to what falls inside and what falls outside of it. And, of course, the Overton window is a natural result of human nature, so it's hard to argue that there shouldn't be an Overton window. We can affect the Overton window, and sometimes we really should try to.