It would depend on who initiated the encounter. If she was the one who goaded him into doing it then yes, he could not consent and could make a report against her, as she coerced him into sex when he was mentally impaired. However, as far as I can tell, nobody was there for the beginning of the encounter and it's impossible to tell who initiated it. The woman was the one who filed the report, but since she doesn't remember what happened, there's no way to know who initiated it.
This is most likely why a grand jury determined that no charges will be filed. Since they were both intoxicated and mentally impaired, it would be irresponsible to try and assign blame to either party. I suppose I shouldn't have said "The man should be held accountable" as holding the man accountable at all times in situations like this would be bullshit and definitely unfair. It would have been better if I had said if he is the one who initiated the sexual encounter, he should be held responsible even if he was drunk himself, same as a drunk driver or a drunk person walking down the street and punching a random stranger should be held accountable for their actions as well. If he did not initiate it though, then he is not at fault. Even with the woman taking the case to the police first, that doesn't imply wrongdoing on his part (or acceptance of what happened) as there could be other reasons, such as him being unaware of the pictures/video. After all, he did say that they were unaware they were being filmed at the time.