Ah. William F. Buckley first says that he defended McCarthy only when McCarthy made baseless attacks on Democratic cabinet members like Secretary George Marshall and his Defense Department, not when Buckley made baseless attacks on Republican cabinet members like Secretary Charlie Wilson and his Defense Department:

William F. Buckley Jr. on Edward R. Murrow, Sen. Joe McCarthy, and Good Night, and Good Luck on National Review Online: [M]y own study of McCarthy ended with his activity in September 1953, that his fight with the Army, which was what the fracas was about in 1954 — which got him censured, and which loosed Edward R. Murrow — was something else, that McCarthy had thrown restraint to one side, that he was deep in booze in those days and did some flatly inexcusable things, for instance his attack on General Ralph Zwicker.....

And then compares Joe "inexcusable things" McCarthy to St. Francis of Assisi:

If there were five million feet of film on St. Francis of Assisi, you could probably find a shot of him running away naked from his father’s house (he did), and Ed Murrow could prove he was an exhibitionist and a poseur (he affected to talk to the birds!)...

Somehow, Buckley also manages to reverse his field, and say--somehow--that Murrow was--somehow--cowardly and--somehow--smeared that Tail-Gunner Joe whom Buckley has just said did "inexcusable things":

Murrow had uniquely the skill to wrest the highest dramatic content out of any situation. There were the bad boys and the good boys; and he was the good boys’ best boy on TV. But more than just that, he did develop a form, he and Fred Friendly, that hadn’t been fully developed theretofore. It went like this: PAN ON FULL FACE OF SENATOR MCCARTHY. He is perspiring and weaving a little in front of a microphone, preparing to speak. No music. Total silence. Then the Senator lets out a long burp. SHIFT TO ED MURROW. “Ladies and gentlemen, this evening we’ll take a look at Senator McCarthy...” That half-hour on McCarthy was Murrow’s most important show. All the obituary writers mentioned it, and the great courage it took to attack Senator McCarthy — which certainly indicated that this is a nation whose people are courageous, since everybody was doing it, or at least everybody who counts. Everybody moral. And Edward R. Murrow was the most moral man on television, because he had the guts to show up Senator McCarthy for what he was...

Cowardly Murrow is thus sharply contrasted with William F. Buckley, who thought in 1954 that McCarthy was doing "inexcusable things," and yet kept quiet, very quiet indeed...

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UPDATE: How big a risk were Murrow and Friendly taking in taking on McCarthy? Certainly their boss, Paley, was scared.

There were, however, lots of Republicans at the time who hoped that Murrow and company would succeed. Joe McCarthy thought that he was doing well (for himself) by attracting press coverage for doing good (for the country) by uncovering "security risks" in government. And Taft, Eisenhower, Nixon, and the other heads of the Republican Party thought that claiming to have found "security risks" in government was a fine thing to do as long as the government was run by Democrats, and as long as it was politically advisable to paint as somehow "soft on Communism" Truman and his advisors--the people who had constructed the Western Alliance and mobilized the U.S. for the two-generation long struggle of Containment.

However, Taft, Eisenhower, Nixon, and the other heads of the Republican Party also thought that claiming to have found "security risks" in government was a bad thing once the government was run by Republicans. They were unwilling to attack McCarthy themselves: that would have made their cynical political calculation too obvious. But they were happy to watch Murrow and company from the sidelines. Were they perhaps also willing to send Nixon to tell the right-wing slime machine not to attack Murrow and company, and instead to let McCarthy twist slowly, slowly in the wind? I don't know.

Certainly nobody told McCarthy that the game had changed: certainly William F. Buckley never told him that the game had changed.