OK this is gonna sound like I'm defending his shitty behavior, which I'm not trying to do. But that said, you shouldn't just dismiss his argument as him being not smart.

My university has a similar problem. About a third of students were cheating in my ochem 2 class and as far as I know, no one was caught or punished. Most of the A's were going to the cheaters, most of the B's were going to the good students, and so the mediocre ochem students like me were left with C's (luckily the university made it so that only 2 or 3 people got an F in it).

And grade deflation is a thing at lots of schools. At my school we start with 800 premeds and end up with only 200 applying to medical school, and only a quarter of those will have mostly A's due to the curve. The university accepts 800 qualified applicants with the knowledge that the curving system means only 50 will have strongly competitive GPA's at the end. And if they only accepted those 50, then only 3 of them would get the highly competitive grades.

Meanwhile our humanities courses aren't curved. That's not to say they're easy; in fact, my cGPA is a fair bit lower than my sGPA. But it's possible for everyone to get an A at least.

I don't know if he's talking about the same thing I'm talking about but a university where 6% of people get good grades I think counts as "actively grade deflating".