Ive got no problem with 'keyboard warriors', mainly because I completely understand the total lack of restraint that is shown between two people that will never meet--even more so when one of them has put themselves in the limelight and, thus, makes it possible for strangers to judge them.
Anyway, somebody calling another a 'keyboard warrior' implies they wouldn't say what was said in person because they'd be scared of getting beaten up, which is just as douchey.
So either respond with words, or shut the fuck up and accept that not everyone can see what a fine specimen you are, or cares that you might be able to physically overpower them should you ever cross paths.
Long live, and power be to the 'keyboard warrior'--exposing the angry bullies that can only resort to violence since the internet was born.