We know it from bullies and we know it from thugs. Once you become a threat to them, they back down. If not immediately, then after beating them twice. It’s pretty simple, once you get the hang of it.
Now, being transferred to the online world, what is a troll afraid of? He is afraid of being stripped of his anonymity, ie shown that he is vulnerable. So next time someone insults you fiercely, you start your doxing game and send them a nice mail with some details about him. If he continues, you make his address public. You continue till he shuts up and others know not to mess with you.