He's also the kind of frothing lunatic who looks at the aftermath of something like the Horus Heresy and says to himself, "What we should do is exactly what I say, regardless of authority, and if we don't do it my way I'LL KILL YOU ALL."

You know, the whole nearly instigating a second civil war right after the Heresy was resolved, thing.

He's exactly the kind of person who it might seem a very good idea to cure. And who it would probably actually be a massive mistake to cure. (Both in and out of universe. He didn't earn the nickname Rowboat Girlyman out of fan affection.