It's actually two paragraphs.

Purging the Left of communists became a longstanding practice, having injurious effects on various progressive causes. For instance, in 1949 some twelve unions were ousted from the CIO because they had Reds in their leadership. The purge reduced CIO membership by some 1.7 million and seriously weakened its recruitment drives and political clout. In the late 10940s, to avoid being "smeared" as Reds, Americans for Democratic Action (ADA), a supposedly progressive group, became one of the most vocally anticommunist organizations.

The strategy did not work. ADA and others on the Left were still attacked for being communist or soft on communism by those on the Right. Then and now, many on the Left have failed to realize that those who fight for social change on behalf of the less-privilege elements of society will be Red-baited by conservative elites whether they are communists or not. For ruling interests, it makes little dif­ference whether their wealth and power is challenged by "communist subversives" or "loyal American liberals." All are lumped together as more or less equally abhorrent.