Let me state outright that I have no doubt Whedon did and said a lot of shitty things about SMG, however it feels like you're just randomly throwing every hint of hostility between the two that you could think of without there being any relation with one another. Him insulting her film is petty and rude, which is different from him reminding her that she has signed a contract that she has to abide by. It's a shitty situation for her but I don't see how this can be construed as abusive or mean spirited in any way. SMG wanted to make movies, he wanted to keep on making the show, their interests diverged, as they often do between actors and producers. It happens.
As to the last part, don't know if it was direct at me, but I certainly do not "scapegoat" Marti Noxon. I love season 6, think this is the closest the show ever got to having a "female perspective" and think her contribution to the show is brilliant, and yes Whedon (and Fury, and others) had the final stamp of approval and sprinkled his stuff as he always did, but having followed Noxon's other works, you can tell a lot of it is her; hell, she (and others) explicitly stated as much. So yeah, she was in great part responsible - responsible for making a pretty amazing season of TV that was pretty trail-blazing in many ways.
The UK was pretty infamous for over-censoring content and honestly, it does not matter. It wasn't the case in my country and the program was aimed at highschoolers (14 yo at the youngest) who grew older with the show. I watched S6 when I was 8 and wasn't scarred for life (ok Anya cutting up her face was kinda creepy).
Ultimately, I'm sorry that SMG didn't have a good experience (though we don't actually know what happened exactly, if it was on the actual shooting side of things or just the story, or both), but I'm not crazy about this trend of blaming writers for not doing what the actors want. The actor not being treated right during the shooting of the scene would be where I draw the line, but AFAIK she has not claimed that was the case. In a ideal world, there would be a more collaborative environment and time to talk things out, but a show on network TV that has to produce 22 hours of content in 2001 is not an ideal world.