The author picked the fight. People are dismissing what he's saying because writing that makes him come across as self-aggrandising. As a result, people are making a judgement call that the guy probably doesn't have much to offer.
To continue with your gym analogy, it's like some weedy guy walking into a gym and telling all the jacked guys that they're exercising wrong and he can teach them better form. That may in fact be true - being able to teach form doesn't require you to be jacked, and vice versa. But more than likely this person is talking out their ass.
I'm 23 and when I read that sentence it totally turned me off the article, the author seemed like a tool, and I completely agree with all the 30-40 yr olds in this thread saying the same thing.
Being 22 is harder if you pass on opportunities to get perspective...
All I'm saying is, all things considered, building a business is hard regardless of what age you are.
That means that more people will face more challenges at the same time as they age. And, more importantly, any individual facing real hardship while young is unfortunately still likely to face greater hardships as they get older. That is why the OP's advice to build perspective earlier in life is useful for everyone, and does not discount the reality of hardship for the article writer or other young people.
Also, I agree that raising kids may be something that is more difficult that you additionally have to do (all the other things have no correlation with age), but some of the replies here come off to me like that one jacked dude in the gym giving the newbies stick for being weak. At their current musculature, they are doing the best they can. Difficulty levels are relative.