It's real, but viewed from the wrong perspective. The overton window is the set of ideas that The general public will find acceptable.

The right have been dragging it right in America (along with the rest of the world). They've done this by joking about various topics, then backing off. Individually, it doesn't make much difference. With the media machine the right have, and a few decades, and we ended up here.

The left chooses to be constrained by it, rather than trying to push it back to counter the fascists.