As long as one of the bullies is sufficiently bloody, maimed, or dead, you'll have accomplished your purpose.
Plus you can chose when to retaliate, every member of a group bullying you can't be with overwhelming numbers all the time, especially at their home and the like.
I too was "different", brilliant, and bullied to more than a small degree early on into junior high (8th grade) ... but I had over the years, starting in elementary school, established a reputation that while I was a generally very nice and good guy, if you crossed various lines there was absolutely no limit to what I'd do to retaliate (note, with a continuum of force, just no upper limit to it). Oh, yeah, I started learning how to shoot in 1st grade, and was very good at it, although I'm not sure if that was clear to others until high school when I was on the rifle team (I certainly never made threats, especially of that nature).
The key, of course, is deterrence. Perhaps it's a Southern (USA) thing; I grew up in a culturally Southern area, one parent raised in it, another from the Deep South, although a skewed version of it, Louisiana and Cajun (French settlers who were forced to leave "Arcadia", a formerly French part of Canada). So unlike this victim, once a line was crossed, I did care about getting my adversaries hurt, that was the objective after all. Let it be cost free and you can see what happens.
Strange anecdote: one day when I was a senior it did come very very close to serious violence, the closest ever, but the adversary ran into a closed off for that period area where teachers were. His complaints that I was armed with a dog choker chain around my right fist fell on deaf ears as I silently and casually put it in my pocket.
I was later told by a school authority that the school would have done nothing to me if I'd beaten him up (!). Back then, at least (1979), I guess it made a difference having a perfect record of good behavior and being college track etc., vs. being a notorious trouble maker and not so bright (come to think of it, pretty much all the other bullies had given up by then).
If you can't bring yourself to retaliate, and it's clear to your adversaries ... don't know what to say or advise. But that you'll lose big time, as this victim did.