In my early college days I took, and failed an intro-level class that I took this attitude toward.

I pointed out how far beneath my current level of knowledge the subject matter was. This wasn't unmerited - even the 2nd time around I sincerely learned absolutely nothing from the class. The only reason I was even there was that the school's backwards policies regarding prerequisites prevented me from testing out of the class. Despite ample evidence, my complaints were disregarded by all as hubris and I had to take the class again, at my own expense.

Turns out, buying the book and showing up did improve my grade! But only because it allowed me to keep track of the amazingly long list of ways the professor was grossly misinforming the class, so that I could mark all the wrong answers "correctly" on the final.

For context, this was Introduction to Computer Sciences at a community college. Day one was literally "how to use a mouse" and I was already a reasonably accomplished young programmer. I should have been allowed to test out.

Eventually, the administration figured out that this guy was an English teacher filling in for someone with an actual CS degree and he was "supplementing" the curriculum with his own misinformation and uneducated opinions. Some of this stuff was "typing google into google breaks the internet" level bad. When this came to light, I was refunded tuition for the class and my transcript was corrected.

Everything he didn't like, use or understand was a virus. OpenOffice was a virus. Linux was a virus. Even google was a virus (he used yahoo). One of the final projects was to build a small web page. I was feeling ambitious and used a little CSS, which wasn't something he taught us, but it was in the textbook and the assignment said anything in the textbook was allowed so... extra credit, right? Nope, he failed me because "that javascript crap spreads viruses."

He gave all his lectures using an old-school overhead projector and acetate transparencies. Including the lecture on PowerPoint. The classroom had a brand new LCD projector, which he couldn't figure out how to use.

I'm not saying this attitude isn't rampant among students who merely think they have the skills to pass the class and actually don't. I'm not saying it's unreasonable to expect students to buy the book, show up and apply themselves...

I'm saying that it's a mistake to assume that these things are always the student's fault simply because they show a little hubris. Sometimes, the instructor really is the reason the kids aren't learning.

TL;DR: It may be the exception to the rule, but sometimes, the student really does know what they're doing and the professor really is the asshole.