Even if it portrays fiction, I think that this should be limited to adult audience still.
Social media, mass media and other types of media can easily be accessed by children these days. If the parents wont be careful and watchful with their kids, they could trigger their own curiosity that will lead them to watch porn.
It serves as a reminder.
I agree. It's always up to the parents regarding how they'd like to limit and/or prevent these sort of things from happening inside they're homes. Granted that these parents are fully aware and are techy enough at least, to figure out what's really best to do, in order to prevent these sort of things to be viewed accidentally by their children.
That is why television shows have a rating and even the films.
Best education and awareness start from home and it's the parent's duty to monitor their children what they've been looking at and what are things that makes them curious. We became child and we know that this is a serious thing.