I'm guessing the list is based on political salience, not just how "bad" a person is.

There probably aren't that many Vlad the Impaler apologists in the world, given that he's a functionally irrelevant person to be an apologist for. That's perhaps less the case for Stalin, but even Marxist-Leninists (seem) to make fewer excuses for Stalin-the-human than neo-Nazis do for Hitler-the-human.