[lucozade]

You're right that Professor 't Hooft is being sarcastic but you've got the wrong target.

He's not aiming this at practicing physicists. He says early on that, if you want to be a physicist, you should enroll at a University. He says in the Questions section that you'll eventually need a degree.

This is aimed at people who can't or won't. The sarcasm is intended to appeal to the "well intended but totally useless" amateur physicists that regularly send him crackpot theories. It's a common refrain from such individuals that they are held back by the establishment.

What he's trying to convey is the amount of information that one needs to master to be taken seriously as a theoretical physicist. His intention is both to put off those that have read a popular science book and now know it all as well as encouraging those that are actually serious by giving them some structure to their learning.