If you read the Bible with that mind set, the stuff about Lucifer reads like a spy thriller about a failed coup, so he has a valid point there.
As for all those liberals having read him.
People ask how "Good Germans" could support Hitler, how "Good Russians" could support Lenin and Stalin, or how "Good Chinese" could support Mao.
First off we ask that with hindsight, knowing what they actually did as well as what they promised, but Alinsky answers the question with a how to manual.
"Rules for Radicals" is to politics what Sun Tzu or Musashi are to war.