Somewhere in most employee handbooks are rules about online behavior.
Those rules don't seem to be working too well. For proof, look no further than the comments people leave under YouTube videos or blog posts or in back-and-forth snipes under news stories. Look at the hateful replies and invective hurled about on Twitter and Facebook.
Internet trolling is ubiquitous in part because it comes with few consequences. You walk up to a woman at work and call her a slut, you get fired, punched or, hopefully, both. You walk up to someone you disagree with and start calling that person an idiot, you get publicly shunned, punched or, hopefully, both.
There are checks and balances...