That's a very demeaning, disrespectful thing for one adult to do to another.
It certainly was, but not for the reasons you mean. They told me because they wanted to make the point that the abuse I suffered as a child was "worth less" than the abuse they suffered as a child; i.e. they used it as an excuse to justify what
they did to me. So it was quite demeaning, really. For me.
People keeping silence about a child molester is something I have some issues with; but particularly when the one they abused went on to screw up my life, too, as my parent. After all, the cycle of abuse has to be broken. I would quite like the person who ruined more than one life by way of what they did to face some kind of justice, but I know they never will, so never mind, I guess.
But that's beside the point. It is an interesting question to ask anyone what they would do. My opinion is colored by the fact I am involved directly in it as a family situation. And in that case you're damned right I'd decide what's best.
If it was some completely unrelated person then no, that's more their business than mine if they're an adult.