No, it's not.

I'm not agreeing that Sinclair is right or wrong philosophically.

Only that they DO own the stations, chose not to air this particular program for reasons that they do not have to explain to you, and chose to air something else instead.

I believe they have a right to air any COMMERCIAL programming that they want to or are network affiliated with. In case you forgot, all you thumping telecommunication lawyer wannabes out there, Nightline is a commercial broadcast. The Sinclair stations are affiliated with ABC and not owned by them.

I love how the same individuals keep crying foul all the time. If you don't like a broadcaster's political view, don't watch them. Or buy your own station and air what you want.