I commend you for continually bringing David Horowitz's very credible explanation of the motivations of leftists to our attention. The essay is so good it should be read in its entirety.
Indeed, one might even go so far as to say that it rivals Witness by Whittaker Chambers as an insider's explanation of what makes leftists what they are and what makes them behave the way they do. Both Chambers and Horowitz are insiders, recovering leftists, who have figuratively been reborn and their descriptions and explanations carry the weight of their own experiences. As such they are invaluable because they are credible.
David Horowitz shows WHY the left is so ruthless . I ask “How do they get the moral vision they have? Once somebody has a moral vision of any kind that is very nearly the last thing you can change about them. That’s the core of the problem, the twisted moral vision they have. At the root of it is the belief that man must be made to serve man.