The last time this came up on HN that I remember, someone linked to these posts by Rick Falkvinge:
https://falkvinge.net/2012/09/07/three-reasons-child-porn-mu...
https://falkvinge.net/2012/09/11/child-porn-laws-arent-as-ba...
That doesn't seem like a strong argument, because it applies to a lot of other things as well, like illegal drugs. (And if the court relies on witnesses to establish that drugs were possessed, they could technically do the same by cp.)
We might find the people watching child porn disgusting but they are after all only watching and not necessarily doing anything resembling rape porn.
They both fall under the same category but they are two very different things.
Also don't forget that a big part of the issue with pedophilia is actually society which because of the tabu and inability to distinguish between the different types of them ends up making the experience even worse and further adding to the problem.
And again I am not in any way defending this behavior, I have kids myself. I just believe that the very thorny subject requires more careful thinking than just calling evil.
I do dislike the OP's guilt by association and vigilantism though. There's a reason we have a proper justice system. Imagine if someone like this was mistaken about one of those email addresses. You could sue him to hell but the damage might be done.