Completely disagree with you. There is nothing more demotivating and infuriating than a professor breezing through challenging material with no acknowledgement that it is difficult.
If I'm learning a semester's worth of new things, and in there 10-20% is going to be discontinuously difficult, I want the prof to acknowledge that fact. I hate feeling like an idiot, and an acknowledgement that a particular topic requires a manner or mode of thinking orthogonal to what I'm used to helps a lot.
You're disagreeing with something I didn't say. A professor should not "breeze through" anything. I just said they shouldn't set up students with preconceptions of difficulty.
If I'm learning a semester's worth of new things, and in there 10-20% is going to be discontinuously difficult, I want the prof to acknowledge that fact. I hate feeling like an idiot, and an acknowledgement that a particular topic requires a manner or mode of thinking orthogonal to what I'm used to helps a lot.