This is all about what tools enable.
This issue is critically important to people who have a much higher privacy need than the average person. Consider an abusive ex tracking down their victim in an unknown new city.
If the profile is indexable, the abuser is trying to either use OKCupid's search (which returns results with a high degree of randomness), or using things like "site:okcupid.com $interest1 $interest2", which is noisy, to say the least. This task looks hopeless quickly.
But if someone provides a database of profiles, the job gets much more tractable. Suddenly, you've enabled the attacker to filter by people who have 1,2,n interests of their ex, search with photographs of their ex, hell, even use facial recognition. Some of these things were kind of possible before, but with a database they are likely. If someone builds a "find your ex" web frontend on this database that uses facial recognition technology, it becomes accessible to everyone, and maybe even popular.
Saying that this lesson should be educational is theoretically nice, but doesn't match how users interact with products in the real world. Anyone who has worked on a product with millions of users knows that the average user (a) doesn't know that there are settings (b) they don't know which things are controlled by settings (c) they don't know how to find the settings, and (d) they don't know how to change them. This is so common that I no longer believe that users are responsible for the implications of default settings (and OKCupid's defaults are, inconveniently enough, Public).
Tools usually are capable of both good and bad things, but a database of profiles has limited upside, and a huge downside. Like, this thing had better be curing a minor fatal disease for the amount of trouble that it will cause.