Of course I'm referring to Ayn Rand and Immanuel Kant. It's relevant to put the two together in one post particularly since Rand considered Kant to be "the most evil man in mankind's history." Basically because he allegedly created the intellectual means by which widespread evil is created, not because he himself was some kind of mass murderer. But then neither was Ayn Rand, who is also thoroughly demonized, sometimes by people who do understand her and by some whose knowledge of her writings is fairly sketchy.
One answer is that neither philosopher is evil per se. They were not psychopaths or sociopaths, or truly anti-social. Rand may have been functionally narcissistic and OCPD, she had an affair with Nathaniel Branden, but she didn't commit any jailable offenses. And Kant, as far as we know, was pure as the wind-driven snow, who died a virgin and who always slept with his hands on top of the covers.
Another answer is that Rand is evil whereas Kant is not, because Rand created a philosophy that allegedly makes evil a possibility by giving it an excuse, and a selfish one at that.