Maybe I should make it clear that I don’t object in principle to sex in anime. If it’s a quality show and the director thinks the story requires the characters to have sex, that’s fine with me. And Lord knows that I don’t object to a bit of cheesecake in an otherwise good show.
I don’t approve of fanservice shows which rely on sex to get people to watch some uninspired drivel that nobody would be interested in watching without the sex, but I wouldn’t normally bother to mention such shows in a blog post. What infuriates me about YnS is another matter entirely, something I would probably find objectionable even if it was a good show in other respects.
So why did I bring up the sex angle in discussing YnS? Because it makes things much more egregious. Without the ending the show would just be salacious trash that would probably not do anyone any real harm. Without the sex it would be boring trash that nobody would watch, even though the episodes would only be 5 or 10 minutes long. With both the sex and the ending you have something that a lot of young people would be inclined to seek out and watch, and which potentially could do a great deal of harm.