He must also be an amazing actor because in all the interviews, commentary, extras stuff I've seen him in he seems amazingly down-to-Earth for someone in his line of work.
Everything in life is relative, I doubt anyone is going to put PCP in the casts food to get even with Joss as has happened with another wildly successful writer/director/producer.
You need a certain persistance of vision to do what Joss Whedon does, I'm glad he has it for what he's given us. I don't know too much about the Charisma thing, but I haven't heard of actors saying they'd never work with him as does happen with the real baddies in the business. On the contrary, people like Nathan Fillion and others seem grateful for the chance to work with him.
One of the things that got me hooked on the worlds of Joss Whedon, is the sense of conscience, moral compass and family that runs through his series. I don't think you can fake that. He also depends on ensembles that work very closely together and he needs to empower his cast and production crew to even make his vision work, that doesn't seem like the style or behaviour of an asshole or egomaniac.
He and his staff also plan out story lines months or in a few cases even years in advance, I can see how he'd get upset if an actor playing one of his central characters did something that threw all that time and preparation out the window. It is a business we're discussing and even though it seems like he creates a family atmosphere with the people he works with, he still needs to deliver a marketable series to the studio. In the case of Charisma, I can see how some producers would have reacted with the old, "you'll never work in this town again". The fact she did come back on the show and worked again on other series shows that's not the case. I believe Charisma was a former NBA cheerleader, with Joss she got to do three seasons with Buffy and four with Angel, most people would consider that a very successful career.
Joss Whedon is now one of the most successful director/writers ever. His only real peer right now is James Cameron, a person some actors and others in the business loath. In the case of Mary Elizabeth Mastrantonio, she credits Cameron with effectively ending her career due to the trauma of being repeatedly beaten by Ed Harris in one scene with Cameron demanding he repeat it and harder. Ed Harris also stated after that film he'd never work with Cameron again. I can't see Whedon even coming close to something like this.
He's human, he's also a great writer and producer who made his name working very closely with his casts and crews in series that did or should have run for years. You can't do that if your style and personality are anti-social.
