he said that he "saw" or "met" God in the Cave, and that The Prophet :saw: "wrote" down the Qur'an, when in fact, it was revealed to him :saw: orally, so he could recite it.
The Prophet :saw: met Jibreel :as: who commanded him to recite the Qur'an. Jibreel :as: got the knowledge of the Qur'aan from Allah :swt: .
It sounded just way too biased coming from his mouth.
I know you said earlier that he says a bunch of things that rub you the wrong way and the way he says them, but just based on this example here it doesn't sound like he said anything maliciously anti islam. Sounds like he just doesn't know the story from the muslim perspective.

Was he covering content that is part of the course material that everyone needs to learn, or was it just an off topic tangent a class discussion went into it? If it was just an off topic discussion I would suggest either ignoring it or approaching him after class and, light heartedly and in a conversational tone point out what he said was "slightly" off.
If it was part of the course content, then I would reccomend doing exact same thing, only add that you're confused why his version of the story is being taught.