And yet in “Good Night, and Good Luck” — the title is taken from Murrow’s sign-off — Murrow comes off as a model of effective restraint, easily threading the needle of a debate that continues today. Though the Air Force’s case against the reservist sounds trumped up, Murrow merely says, “We do not know.” (The man was reinstated a month after the episode.) The main broadside against McCarthy, aired on March 9, 1954, consists almost entirely of the senator’s own words from recordings and transcripts of speeches and congressional hearings. Even so, “See It Now” gives him an entire episode to respond, during which he falsely asserts that Murrow has been on the Soviet payroll for decades. Murrow’s follow-up, a week later, is a classic just-the-facts takedown.

Of course, as we know, McCarthy got what he deserved: He was censured by the Senate that December, becoming a pariah and dying in office. Murrow got what he deserved, too: secular sainthood.

But I mentioned martyrs, and there is one in the play: Don Hollenbeck, a CBS colleague hounded mercilessly by McCarthy surrogates. Whether his fate was tied to that hounding — well, to quote Murrow, we do not know. But the play makes the case, in the way plays do, by giving an excellent actor (Clark Gregg) big emotions to play.

I wish “Good Night, and Good Luck” were more often so subjective. Instead, influenced by Murrow’s example, it keeps things mostly cool and concrete. (McCarthy is not played by an actor but by himself on tape, leaving no room for editorializing.) Probably this was wise; when the show suddenly gets hot at the end, with a montage of television news since the 1950s, it feels overheated. Preachers preaching to the converted usually do.

Yet preaching to the converted can be a good role for theater. So is rousing the demoralized with the example of heroes who have prevailed. Clooney’s refusal to grandstand as an actor allows his Murrow to maintain his halo. These things were possible, the play seems to say; they can be again. No matter that with only three networks and enormous national viewership, the television news of Murrow’s day was much more influential than it is in ours. “Good Night, and Good Luck” is a powerful and useful reminder that a demigod, or maybe it takes many whose names we don’t know, can still sometimes bring down a devil.

Good Night, and Good Luck
Through June 8 at the Winter Garden, Manhattan; goodnightgoodluckbroadway.com. Running time: 1 hour 30 minutes.