I found a great quote from Lincoln:
“Quarrel not at all. No man resolved to make the most of himself can spare time for personal contention. Still less can he afford to take all the consequences, including the vitiating of his temper and loss of self control. Yield larger things to which you can show no more than equal right; and yield lesser ones, though clearly your own. Better give your path to a dog than be bitten by him in contesting for the right. Even killing the dog would not cure the bite.”
XKCD has, as always, already covered this years ago.
Update: There actually is research about how internet trolls are changing other readers perception of the actual content.