Dalton Trumbo is in trouble again.

Sixty-eight years after he went to prison and 39 years after he died, the famous/notorious Hollywood screenwriter is once again being denounced as a fervid Stalinist or lauded as an admirable man of great principle. Trumbo, who wrote while soaking in the bathtub and sipping the muse of Scotch whiskey, would have exulted in his renewed fame. A dandy movie about him has just been released. It’s called “Trumbo.” He would have approved.

Dalton Trumbo was at the top of his game when in 1947 he and nine other screenwriters went to prison for refusing to testify to Congress about their political views. When the so-called Hollywood Ten were freed, they joined a long list of movie industry figures — writers, actors, directors, etc. — who were blacklisted for their supposed or actual communist ties or sympathies. If they had been Reds in the past, they were required to recant — and to identify and denounce those who also had been. Some never worked again. Some worked under aliases.

Trumbo won an Academy Award for the movie “The Brave One” writing as the nonexistent Robert Rich. He used the name of a cooperating fellow writer, Ian McLellan Hunter, to get an Oscar for “Roman Holiday.” His most interesting film, if you ask me, was 1962’s “Lonely Are The Brave,” starring Kirk Douglas as a modern-day cowboy furiously at odds with the 20th century. Two years earlier, Douglas — not just another pretty face — had busted the blacklist by insisting that Trumbo get credit for writing “Spartacus.”

By 1960, the so-called Hollywood blacklist had collapsed. The shameful era did not last long, but it did plenty of damage. Careers were ruined, families came apart and genius was frittered away. It was a brief period, but it is not yet over.

Nowadays, accusations of racism or sexism are the functional equivalent of what accusations of communism used to be — an anathema that fires up the mob and produces calls for punishment. All one has to do is veer a bit from orthodoxy. Susan Brownmiller, 80 years old and in her day a radical and highly influential feminist, was recently nearly tweeted to death as a slut-slammer for saying that women can’t really drink as much as men.

At the moment, an online petition, signed by upwards of 30,000 people, is calling for the head of CNN’s Don Lemon. He had the temerity to question whether that now-infamous school cop in Columbia, S.C., used excessive force in heaving a student out of the classroom. From what I could see, he did, but I wondered at the time just how you handle a disorderly student who refuses to budge. No matter. Questions not permitted. The petitioners demand that Lemon be fired.

Something similar happened to George Will last year when he took up the matter of campus rape. He was instantly denounced by the National Organization for Women which demanded that The Washington Post “dump George Will now!” The undumpable Will remains a fixture of The Post’s op-ed page where, twice a week, I invariably disagree with him.

Trumbo was a man of stern principles. He could have testified to Congress as others did — the film shows Ronald Reagan and Robert Taylor doing so — but he believed that the government had no business asking him about his political beliefs. He was, after all, not accused of treason or spying but of having views that too often coincided with those of Joseph Stalin. Somewhere in the Constitution, however, is the glorious right to be a dope.

Trumbo was indeed a communist. That was — and remains — perfectly legal, but it does not stop us from asking what was he thinking? By 1943, when he officially joined the party, the hideous human rights abuses of Stalin’s regime were well-known. In 1939, Stalin concluded a nonaggression pact with Hitler and invaded eastern Poland, murdering many thousand Polish intellectuals,  army officers and priests. American communists such as Trumbo shamefully went along.

Frank Tarloff was another blacklisted screenwriter. Some years ago, his son, Erik, spoke at an event memorializing victims of the blacklist. He quoted George Orwell’s dictum from the novel “1984” that “freedom is the freedom to say that two plus two make four.” Tarloff expanded it. “I think that freedom is the right to say two plus two make five,” he said. “Freedom … is the right to be wrong.”

Trumbo had every right to be wrong. Don Lemon, George Will and even me on occasion have the same right. Somehow, the urge to censor and to demand conformity, has moved from right to left where the most innocent — and yet obligatory — questioning of orthodoxy (such as the martyrdom of Michael Brown) doesn’t bring a response or a rebuttal, but first a labeling (racist, sexist, whatnot) and then the demand for a silencing. It is impermissible for so much to be impermissible. A little discussion is in order.

Dalton Trumbo may once have been what was called a “useful idiot” — someone who could be used by the communist movement. But his usefulness today is to remind us of what can happen when the response to dissent is the swift application of an ugly label and the the application of a gag. In that sense, the blacklist isn’t quite history. In fact, it never went away.