As Welch begins to back McCarthy into a corner with his own stories about why Fred Fisher shouldn't be maligned, McCarthy responds mostly with…vagaries. In particular:

The foremost legal bulwark of the Communist Party, its front organizations, and controlled unions, and which, since its inception, has never failed to rally to the legal defense of the Communist Party, and individual members thereof, including known espionage agents. Now, that is not the language of Senator McCarthy. That is the language of the Un-American Activities Committee. And I can go on with many more citations. (McCarthy.99)

This quote is a great example of one of McCarthy's smears. What you'll notice here is that at no time does he flat-out call Fisher a Communist. No, he was a member of an organization with Communist ties. How about some proof? Oh, sure, McCarthy has a ton of proof, but he's not going to bring it up.

He could, but he won't.

There is little to nothing there you can actually fact-check. In that way McCarthy can skirt the truth and say whatever he likes.