I'd have to find some evidence that McC did persecute Marshall and that he did smear the entertainment sector. I'd have to do some reading and get back with you.
How brave was McCarthy? What effect did he have on the political debate in the United States? You say you need proof that McCarthy went out after George C. Marshall...this from an Eisenhower site....
http://www.eisenhowermemorial.org/stories/Ike-Wisconsin.htm
"One of the best known and most notorious members of the conservative faction within the Republican Party was Senator Joseph McCarthy of Wisconsin. Through his position as a member of the Senate Un-American Activities Committee, he had become nationally famous by publicly denouncing various people as “communist sympathizers” or “downright traitors.” Eisenhower was repulsed by McCarthy’s reckless claims. Ike lamented the Senator’s abusive treatment of witnesses before the Committee. But Eisenhower also believed he needed the electoral votes of Wisconsin to win the presidency, and he did not speak publicly about McCarthy’s activities.
Silence worked for a time, but Eisenhower was trapped by circumstances he should have avoided. Early in the presidential campaign Senator McCarthy issued a scathing condemnation of George Marshall, who had served as President Truman’s Secretary of State after retiring from the Army. The Senator said the former Chief of Staff was, “part of a conspiracy so immense, an infamy so black, as to dwarf any in the history of man.” This was absurd, but in 1952 it was dangerous to point out how absurd McCarthy’s charges were, especially if you were the Republican candidate for president.
Working in his campaign train in Illinois, on his way to make a September 2nd speech in Milwaukee, Eisenhower amended his campaign speech to include a paragraph soundly denouncing the junior Senator from Wisconsin for having bizarrely defamed George Marshall. One of the campaign staffers notified McCarthy of Ike’s intentions. The Governor of Wisconsin, Walter Kohler, and Senator McCarthy flew to Peoria, Illinois, to confront Eisenhower before he got to Wisconsin. Ike met privately with McCarthy and the General told his staff that he had made no commitment to delete the paragraph condemning the attack on George Marshall.
The next day Eisenhower’s future Chief of Staff, Sherman Adams, met with Eisenhower after Governor Kohler told him that including the paragraph in the speech would cause serious problems for the Republicans in Wisconsin. When he sat down with Eisenhower, Adams urged him to take out the paragraph rebuking McCarthy. Adams, whom Ike respected for his political acumen, managed to convince Ike to make his statement on behalf of Marshall later in the campaign -- in a state other than Wisconsin.
But the trap had already closed. Unbeknownst to Eisenhower or Sherman Adams the original text of the speech had already been given to reporters. They waited in Milwaukee, eagerly composing headlines to use about Eisenhower’s stinging condemnation of McCarthy. With Kohler and McCarthy on the platform behind him, Eisenhower delivered his usual campaign speech without the paragraph he had written or any words about either Marshall or McCarthy. His single reference to the matter was a lame and oblique sentence, “The right to question a man’s judgment carries with it no automatic right to question his honor.” When the speech was over, McCarthy was photographed shaking hands with Eisenhower."