I'm going to assume this isn't a meme and you're serious. Do you mean bodybuilding is a mental illness for some by the phrase "to some extent"? Or to everyone at some level? If you mean the former, I agree, mostly with the people that don't compete or make money from it and do it. They likely have some form of body dysmorphia. If you mean everyone who does it ever, that's where there's no way you're right. Some people would have simply done something else if you couldn't make a living bodybuilding, like play another sport or some job where it's extremely competitive. Unless you think people at the top of any field "have a mental illness to some extent" by definition. I don't think bodybuilding is any crazier than say being an MMA fighter in the UFC or a football player in the NFL.