Is the .to (Tonga) domain completely rogue and should be removed?

So what you are saying is that Barry has a perfectly functional
method of dealing with the problem and all the rest of this is a complete
and utter waste of our time.
Mr Sobol's comments doubly so, as they add no new information.

Where do you see him saying that? I don't think either your solution or his
will work.

With spammers, *nothing* works 100%. Even killing their link. It took a
long time of concentrated effort to get Spamford bounced off the net.
Mostly, they just pop up somewhere else. So what if you get TO deleted, big
deal. Those spammers will simply move on. The only thing we can do is work
on reducing the forgeries so they can be more easily filtered and GET THOSE
RELAYS CLOSED. Everyone, running sendmail, should be at v8.9.1 and
subscribed to the RBL, IMHO.