I think the parent's point was that it might seem questionable to find penises and vaginas disgusting.
There is a healthy reason to find feces and defecation disgusting - feces carry diseases and are a waste product. Sexuality is not.
I think it's a bit unhealthy to find penises and vaginas disgusting, but I wouldn't want to discourage somebody from talking about how they feel, if that's how they feel.
If we want to encourage more openly talking about sex, perhaps it's only fair that we also support people openly talking about what they find disgusting.
There is some healthy biological basis behind a disgust reaction to either, as genital contact carries diseases too, depending on how it's done and the history. In that regard, handling faeces is quite similar to close encounters with gentalia - either can be safer or unsafe depending how it's done, and both are a natural part of life which is healthy in moderation.
Equating having sex with what is a completely normal bodily function we have to do once a day was indeed a bad choice of words.
So according to your way of seeing things we should be openly talking about how we fuck, how I'd like to fuck you, how I got fucked by that guy the other day. No thank you. Keep it to yourself. There's no middle ground. What would the middle ground look like? I want to put my pee pee in your poo poo?