At first, my natural inclination was to dislike you. The professor comes off as an asshole.
On the other hand, the student was taught a lesson in a harmless way. Anyone who wants to go into business needs to be able to handle egotistical assholes who make this professor seem saintly by comparison.
In my opinion (as pointed out by lucifer already) the ""xxxx, get your shit together." and following paragraph are quite likely to be the most important lesson the student will learn in his entire academic career.
The professor wrote a highly memorable obviously personalised letter to the student teaching that.
Without outside evidence of "egotistical assholishenss" from the prof (which _may_ exist), I'd read it as an intentionally exaggerated reaction with a solid grain of cold hard truth.
On the other hand, the student was taught a lesson in a harmless way. Anyone who wants to go into business needs to be able to handle egotistical assholes who make this professor seem saintly by comparison.