Christian is a plain coward.
A 90 lb. girl could yell at him and he might tardrage, but flee.
Doesn't matter if she's passed out.
Chris is an autistic too shy to even talk to women. I'm not saying he would have moral objections to taking advantage of someone sexually.
I'm saying he would not have the presence of mind to do it in all but the moist outré and impossible scenarios. Which he is even less likely to get into than others because he is very sheltered.
Once Chris is given the go-ahead, like with Catie, he feels entitled. He's really creepy and grabby. And he's very quick to pick out social cues he interprets as the go-ahead. He'll quickly decide that something's a date, and if it's a date, then they're considered "dating". And if they're dating, then they're boyfriend and girlfriend. And if they're boyfriend and girlfriend, they can have sexy time.
At no point is Chris thinking, "fuck that bitch, I'm gonna rape her", he's thinking "she's my girlfriend, I can kiss my girlfriend, right?"
And this escalation from "just friends" to "boyfriend/girlfriend conjugal rights" isn't just theoretical. Every time this situation comes up, Chris aggressively moves his weird understanding of the relationship ahead without the girl having any clue what he's thinking.
Now, the question is, is Chris so far gone that he'd rape a girl who's completely knocked out?
I think it's unlikely. I don't think Chris is that balsy. However, it's not that far out of the realm of possibility. I'd say maybe 1/16 chance of that.
Now, what's a lot worse is that it's very likely Chris would kiss a passed out girl and fondle her. That's a lot more worrying because it's a lot more likely to happen.
Edit: Although, that's just likely in the context of Chris dating or socializing, which obviously doesn't happen.