Should "sex" be separated out of "social?"?

From time to time efforts to somehow make it easier for people to avoid “sex” as a topic emerge here. Fluther, of course, puts “NSFW” on topics deemed to be sexual in nature, but apparently this isn’t enough. There are calls for a further separating out from time to time.

Why should there be a separate section for discussions of issues of sex? How would you define sexual issues?

If “NSFW” isn’t going to work, then how would having a sexual section keep people from looking at what they don’t want to see?

Would it be possible to separate out “adult” themes from “sexual” themes? If so, how? Are you like the supreme court: you know it when you see it?