Trolls are solitary attention seekers. They are individuals who feel ignored and unheard in real life situations, so as a way of validating themselves they manipulate others via their keyboards. They write things with the sole intent of getting a reaction, and THAT means triumph as far as they’re concerned. To get others involved in their drama is the ultimate validation for them. Nothing feels worse to a troll than being unnoticed.
Your responding to a troll hands them the victory they seek.
Your responding to a troll provides them the attention they desperately crave, which only drives them onward to state even more outrageous things. If no one listens, if no one responds, if their words are rejected as unimportant and irrelevant, the troll will go away. Being ignored is the ultimate indignity for a troll. With no one listening, there will no longer be any motivation to shout. It’s akin to being the sole resident of a ghost town. Any response to a troll provides them with the gratification they so aggressively seek, so the very best way to respond to a troll is not at all.
An online troll, once he makes his outrageous comment, sits back and waits with bated breath for the responses to pour in. How very gratifying to see when no one has taken the bait, no one has responded, to know that this pathetic little person is sitting there waiting, deflated and ignored. But that’s okay — trolls have nothing better to do.