A scene from “Zero Dark Thirty.” (Columbia Pictures)

Why are some of the Senate’s most prominent members seeking to intimidate film studios and writers from discussing an issue of critical national importance? That’s my question after reading the intemperate letter sent Wednesday by Sens. Dianne Feinstein, Carl Levin and John McCain complaining about the depiction of torture in the film “Zero Dark Thirty.”

“The use of torture should be banished from serious public discourse,” write the senators. I agree with them that torture should be banned. But banishing public debate about it? That sounds like censorship. Surely that’s a position more suitable for an authoritarian government than a nation that cherishes the right to speak, even about unpopular topics.

Politicians don’t like ambiguity. They want to insist that torture is not only wrong, but that it’s ineffective. “We believe the film is grossly inaccurate and misleading in its suggestion that torture resulted in information that led to the location of Osama bin Laden,” insists the letter.

The film is more nuanced and ambiguous about whether information obtained after the use of “enhanced interrogation techniques” helped targeters find Osama bin Laden’s courier, and then the al-Qaeda leader. So is the CIA’s own reading of the evidence, based on administration officials’ comments. They’re against torture, too, but they think it’s a mistake to soften the edges of the debate by suggesting that it didn’t provide useful information in the hunt for bin Laden and the broader fight against al-Qaeda.

As I wrote a week ago, after talking with officials about the interrogation record, we should oppose torture because it’s morally wrong, not because it doesn’t work. Politicians need to be honest with the public that this correct moral choice involves some risks.

Here’s how Leon Panetta, then director of the CIA, summed up the evidence in a letter to McCain a week after the May raid that killed Bin Laden: “Some of the detainees who provided useful information about the facilitator/courier’s role had been subjected to enhanced interrogation techniques. Whether those techniques were the ‘only timely and effective way’ to obtain such information is a matter of debate and cannot be established definitively.”

What adds to my worry is that Feinstein, the chair of the Senate Intelligence Committee, last summer introduced an anti-leak bill that leaders of the intelligence community found misguided — because it would chill the very conversations between journalists and government officials that might prevent disclosure of information that would harm the nation. Add to that McCain’s recent jihad against U.N. Ambassador Susan Rice for repeating on television “talking points” prepared by the CIA. You have to wonder if the senators’ real target is the intelligence community — and beyond that, the kind of public discussion that leads to good policy decisions?

No more bullying letters to artists, please, arguing that subjects should be “banished from serious public discourse.”