If something terrible is posted online and it is true but it hurts nobody if you take it down, it seems like common courtesy to not repeat it. You have to weigh the public interest versus peace of mind for the individual. It's not clear cut and dry.
There are things you choose not to say in real life, even if the are true. Just because something is on the internet does not preclude you from that courtesy and respect. Technical reasons (such as caches) can be used as an excuse to act respectably. You do not go around telling colleagues at work about what other colleagues have done. What would you have to gain?
Imagine if you had relations with someone and it was recorded online. The allegations might be true but who has more right for that information to be left up there for all to find? Should you be allowed to post all you like about others, disregarding the potential effects on that person? Or should you be thoughtful about what is in the public interest?
Now imagine a site that records who had relations with whom. There is no maliciousness in this one: it's more of a public record or encyclopedia. Do you have the right to opt out of it?
To go further with my example. Imagine having a sexually transmitted infectious disease. Is the answer the same?