Mmmm... murderous drug-filled rampage.... isn't that what we've been waiting for all of our lives? Ah, the anticipation of the freedom to wreak havoc and leave my burning footprint upon the throat of the world!
Really, morality is unconnected to this kind of thing. It's like saying an atheist is prone to be a villain because he doesn't believe in some sort of dominating moral reality. Yet that's not how it typically plays out. Villains and heroes reside in all ranges of the spectrum of belief -- from the ultra-religious to the purely deterministic. I can have doubts about the validity of the self as an objective entity, but apparently it hasn't changed how I live; in fact, I find myself more compassionate and other-centered than at any other time in my life.
(for what that is worth.)