I expected that the bit about how knee-cappings, tarring and featherings and punishment beatings were not always strictly reserved for drug dealers or often aimed at those competing with the IRA/loyalist's own pushers would be the bit that was ignored. Nice fantasy, horrible reality.
I'll start by saying I think that (
most, other than drugs like antibiotics, which when abused can reasonably be expected to cause a grotesquely disproportionate harm upon others than the user or his/her dependants) drugs should be legal and treated as we (Americans) treat alcohol, legally speaking.
That said, If he was really a drug dealer I feel no sympathy for him. His deliberate illegal trade in something which engenders murder and mayhem of innocents (due to it's illegality, I believe) makes him beyond my sympathy.
Now
who really did the tarring and feathering? I'm afraid I had exactly the same question as you have Ian, when I read the article. If it was neighborhood "vigilantes" who are upstanding citizens, and knew for sure he was a drug dealer, "Good on them". Just as likely I think (and I suspect you think), was that it was other drug dealers who didn't like him taking their business.