"Prank" is a very vague term, though I wonder if a lot of the most objectionable things being discussed here even qualify.
Relentlessly antagonizing and intimidating strangers and recording their exasperated reactions for the amusement of an audience doesn't strike me as a "prank". There's no joke element to it at all, it's just acting outrageously for the sake of attention.
Thinking about some of the most noxious forms of "prank" streamers and it's basically people intentionally provoking a fight with strangers.
That has been my contention all along, yes. As an analogy, it's like asking "what do you do if someone
touches you?" (And no, I'm not doing an argument from analogy. It's just for illustration purposes.) Well, a touch can be anything from someone accidentally bumping into you on the street or being pressed against you in a crowded train, to someone punching you in the face, to someone 'touching' you with a knife or with their dick. There is no single concrete
* answer covering all that.
Again, it's not an argument from analogy. The argument can be made on its own that a "prank" covers everything between stuff pretending to sneeze and blow a garbage bin away (actual example), to someone pretending to throw your toddler over the railing from second floor (look it up, the video actually exists), to calling in a fake bomb threat or emergency (historically, LOTS of people found it HILARIOUS to call in a fake emergency as soon as telephones were introduced), to something that genuinely looks like an assault or kidnapping attempt to a reasonable person. It's a VERY wide spectrum. There is no one answer that fits all.
Is deadly force a reasonable response when someone just sneezes 3m (about 10 ft) from you and blows away a couple of garbage bins? No, because there was no reason to assume any imminent danger to your person. Nothing there is aimed at you. He's not threatening to sneeze/fus-ro-dah you into Shor's Hall or anything.
Is it a reasonable response when a clown charges you with a bloody machete? Yes, it damn well is. It fits the exact legal definitions of assault and of self defense. Which rely on just: did you have reasonable grounds to expect imminent harm? As in, it doesn't matter what the assaulting guy was thinking, it doesn't matter what your actual intelligence is, would a reasonable person of average intelligence interpret it as imminent danger?
So yeah, I think the question in the thread title and some of the generalizations done along the way are really (perhaps unintentional) equivocations, by way of backing up into the super-category that includes a lot of milder cases. It's just not useful to expect a single reasonable response for something that ranges all the way from someone charging you with a machete, to someone peacefully reading a flaming book next to you.
* as in, not something as generic as "it depends."