I'm saying that the discourse on Facebook has expanded the Overton window so that fascist ideas have become much more mainstream. The Wikipedia article (and the sources) talk about moving or expanding the Overton window, not on contracting it. I think the concept of a contracting Overton window is used to make a subtle jab at political correctness. In reality, in the last several years, toxic discourse has been on the rise.

The window is measured in size and location. A window that includes fascism can be big or small, but is likely very far to the right.

Similarly, a window that includes legalizing cocaine while banning political speech would need to be very large, ranging from far left to far right.