Surely there's also an element of an even worse fate hanging over the person getting the treatment, if someone sets light to the tar and feathers? I have the impression that this was not unusual in the KKK version.

...............

In another context, there's an echo of something not a million miles from tar and feathering in in a traditional story, The Devil and the Feathery Wife", in the DT. Here are the relevant verses:

..."Oh, never you worry," his wife, she cried,
"Be it happens, you'll pay for your fee,
For the wit of a woman, it comes in handy
At times in an hour of need

"Go and fetch me the droppings from all of our chickens
And spread them all over the floor
Stark naked I will strip myself
And I'll roll in it all over the floor

"And fetch me the basket of feathers," she cries
"Of the beasts we had for our tea
And I'll roll and I'll roll all over in them
Until never an inch be free"

So she rolled and she rolled in feathers and droppings
from her head down to her navel
"By Christ", he says, "what an horrible sight
You look far worse than the Devil"...