The emphasis is because he wrote two articles: "How to become a good theoretical physicist" (http://www.staff.science.uu.nl/~hooft101/theorist.html), and "How to become a bad theoretical physicist" (http://www.staff.science.uu.nl/~hooft101/theoristbad.html).

Later, the advice on how to become "good" was re-designed to look better, but split the content across multiple pages (http://www.staff.science.uu.nl/~gadda001/goodtheorist/).