I second this request. I have received hate by PM from the "usual suspect" and his sockpuppets. I would also like the functionality of "ignoring" users.
The problem is anonymity, if the users would give their real name or call sign, the problem would be smaller but not disappear.
Everyone can of course decide for themselves whether they are reading a personal message or not, simply not opening or deleting it.
I read personal messages because if I block personal communications as a matter of principle, I miss the chance to meet new people.