I agree that most of the time bullies are indeed covert cowards trying to raise their own self-esteem by standing on you and beating you down.
But in some cases the bully is mentally ill and dangerous: if you stand up to him or her, fight back, try to defend yourself, try to run away... they will beat you even worse or (worst case scenario) try to destroy you, literally: kill you.
I was raised by a mother who was mentally ill (she had at the time as yet undiagnosed, untreated borderline pd) and when I was little if she triggered into a rage at me and I cried or begged or tried to get away it was like throwing gasoline on a fire: it enraged her more.
(Mother almost killed me on a couple of occasions.)
All I could do was go numb and limp like an inanimate object as she gripped my upper arms and screamed her rage from inches away, pupils dilated to solid black, red-faced. I could feel her spittle hitting my face. The screaming was accompanied by physical abuse most of the time.
I think that those who bully and harass and intimidate their target out of obsessive sexual feelings are dangerous also. Very dangerous, in fact, and particularly so for boys.
For example, say if an older, larger boy feels sexually attracted to a younger, smaller boy and feels deeply shamed by these "sinful" feelings, the repressed homosexual may in his mind begin to blame the other boy (or blame gay males in general) for "making" him feel these unacceptable sexual feelings "against his will."
So the repressed homosexual (in a state of deep denial) begins to feel justified and entitled to punish anyone who makes him have "bad" sexual feelings.
This projection and blaming can result in the repressed homosexual male bullying, harassing, tormenting and beating the smaller male severely or even killing him.
I think this was probably the underlying dynamic of the incident in which Omar Mateen shot dozens of gay men to death in the gay nightclub incident last year.
Mateen could not tolerate the incompatible truth about himself: he could not be a "good Muslim" if he also had sexual desires for other men.
In his sick mind the only way he could resolve this cognitive dissonance, absolve his own sinfulness, please Allah, and earn a place in paradise, was by executing as many gay men as possible before committing "suicide by cop."
So, if there is a way to figure out if the bully or bullies harassing you are the garden-variety cowardly type or if they are actually the dangerous, sadistic, mentally-unbalanced, homicidal-monster-type, that would also be very useful.