I'm firmly on the side of the corporate career, but this is a BS argument for it. The outcomes aren't binary. Even if you don't "make it" as a writer / actor / cartoonist, it doesn't automatically mean you're broke and waiting tables well into your forties. You can find yourself part of a well-paid production crew or as a grip or something that you're better suited for that the industry actually needs.

Similarly, if you're doing startups, failure doesn't go on your permanent record and you can try again. These career fields are about choosing your priorities in life, that's how you choose one path or the other.