Full Idea
As for sex, everyone agrees that, while it is extremely pleasant, it should be indulged in (if at all) in secret, because it is a highly contemptible sight.
Gist of Idea
While sex is very pleasant, it should be in secret, as it looks contemptible
Source
Plato (Hippias Major [c.382 BCE], 299a)
Book Reference
Plato: 'Early Socratic Dialogues', ed/tr. Saunders,Trevor J [Penguin 1987], p.257