Stories like these make me so boiling mad! These bullies are not able to carry on their bullying ways because you're weak, they get away with it because you're NICE.
They're exploiting a positive characteristic of yours, so if you want to counter them, you have to go against your own better nature and if you do get into a confrontation by not being nice towards them then the dice is loaded in their favour because they've had YEARS of experience not being nice.
This reminds me of the film Wargames: The only way to win is not to play.