An affliction that causes people to say things to people over the distance of an
Internet connection that, if they ever DARED to say to a person in a face-to-face
conversation, would likely result in them getting knocked on their ass and maybe a trip to the hospital, but behind the safety of their monitor where nobody can physically touch them, they can behave like complete and utter shitbirds with no consequences, because as we all know,
the Internet isn't real, of course, and the person you're mouthing off to isn't a real human being, with emotions of their own.
It is closely related to the similar affliction that causes people to become total sociopaths when behind the wheel of a car, where they are similarly safe from physical retribution.
If the technology were invented tomorrow to make it possible to punch a person
in the face over TCP/IP,
Internet Badass Syndrome would vanish almost overnight, and
the Internet would be the most civil, polite place ever.