there is data that is only available if you are a member of the site and answer questions on the site. for example if a question asks you, "would you date a smoker?" if you answer you can post it so other members can see what you answered to gauge whether what you picked matches with what they liked. what this guy did was go through all the questions and answer them at random then scraped the data that was available only to actual members of the site.
as for profiles being "public". they can be "public" in the sense that you can go to a url and see their profile, yes. but most people set it so only people who have signed up can see them. so by doing this he most likely violated the TOS of the site and scraped the data without permission.
edit: it is not as though it was public, the guy who scraped the data made effort to log into an account, answer all the questions and then _scrape_ the data. it's not like that data is plainly visible if you go to someone's profile.