What "public warning"?
Herb Block was interviewed by Brian Lamb on 14th November, 1993.
Brian Lamb: Here's a cartoon from the year 1950 -- The headline on it is, "You mean I'm supposed to stand on that?" And right up here is the word "McCarthyism." Did you invent that?
Herb Block: That's the first use of that word that I know of and I remember how it originated because I wanted to put something on that tar barrel and you couldn't call it McCarthy himself, and you wouldn't say McCarthy techniques or so on and I thought, "Well, maybe just use one word, McCarthyism," and, you know, it caught on.