I agree with him, though. You have to be very malleable if you're going to be a celebrity. If you insist on keeping even one trait, then you get the equal and opposite reaction of being type-cast for the rest of your life (like Zach Gillifinakis being the perpetual off-the-deep-end, passionate and sweet but ignorant and abnormal pot-smoker guy.) Which of those traits are actually even a part of who he is? maybe all, maybe only one or two, but he'll NEVER be taken seriously now, and he's stuck. For his whole life, even if, as a person, he were to change completely. There is no change, growth, nor redemption for actors. Only type-casting, or nothingness. A projector screen for what people want to believe you are.
Also why their relationships suffer.