Profane words can definitely be drained of their power when overused in a screenplay. That’s a cool example of it being powerful though. In Braveheart the word has power for the reasons you described, it was effective because of it’s context. It takes you off guard and there is a comedic element to it. Where I find the language in Raging Bull is more a reflection of socio-economic characterization. This is who LaMotta is. This is a man who makes a living pummeling other men. He is speaking the only way he knows how. Sometimes hostile, like a caged animal. Do I think it takes away from the film? Not at all.

At the end of the day there is one author of the film, the director. I think that Paul Schrader is a very talented screenwriter but Scorsese made the film his own as he did with their other collaboration, Taxi Driver.

A little sidenote: in the original screenplay, Schrader had a scene where LaMotta was locked up in a Florida jail cell. That scene is in the film but what Schrader originally envisioned was LaMotta trying to masturbate to the thought of his wife. He can’t because he is so filled with rage. DeNiro and Scorsese weren’t having it and had Schrader rewrite it. It would have been a very different scene to say the least.

Writers can certainly make “fuck” a dead word. After a few thousand “fucks,” it has no power. As a writer, why would you want to lose this power? A lot of people seem to develop a case of Tourette’s when they start to write.

I like its use, though, when it’s used in a movie by a character or in a moment that you would not expect it. For instance, in this battle scene from Braveheart:

As arrows fly from the English bows, the Scots crouch behind their
shields.)

Stephen: (To Wallace)
The Lord says He can get me out
of this mess, but He’s pretty
sure you’re fucked. Ah!

I wasn’t expecting to hear it in 13-century Scottish dialogue. Couple that with the idea that He would think anyone is “fucked,” it’s a moment of dialogue that’s stuck with me.

Anyhow, thanks for the shout out! And good luck on your script there.