I taught at USMA for 4 years, including the last one as a civilian, ending in June 2017. I'm not a West Pointer, so other than my experience there as an instructor I have no bias.
That guy is as wrong as two brothers ****ing. Are there problem cadets? Yes, of course. But the level of problems, and the severity of those problems, are not nearly as bad as that passed-over-for-O6-and-force-retired guy says.
I taught some of the brightest and most respectful students I've ever met. I taught a few dirt bags, but when I had a dirt bag I'd send an email to his/her TAC (captain/major who is that cadet company's legal commander) and the problem would be resolved. The issue with some instructors, including what I've heard about this guy from students and instructor friends whose opinions I value, is that they try to recreate their glory years in the classroom. If you try to act like a drill sergeant in an inane history of Russian foreign policy class, you're going to get a lot of apathy.
There is indeed some "academic dishonesty" but it's dealt with pretty well, I think. I was a on the cadet honor board as a senior at A&M (2004), and I promise we had absolutely zero impact on anything. The USMA honor board cadets actually make recommendations. The process takes literally forever and is bureaucratic as hell, but it's taken more seriously than in the Corps at A&M (remember the exam files? that's cheating).
Cadets were booted out, turned back a year, sent out to the Army for 2 years to grow up and then reapply, or summarily executed regularly. I'm not a huge fan of LTG Caslen, and it is true he's sacrificed a lot upon the altar of winning football games, but the whole joint is not falling apart. Honestly, that letter is so trifling it doesn't deserve much of a response, although Caslen did write an official response that was published somewhere.