Email: CC and Reply All
I understand that some people aren't computer experts, but for email, that's like understanding that some people used to publicly have sex with monkeys. Back then, people and monkeys weren't such different concepts. We're past that stage now. And anyone still doing it is just spreading horrible things among the rest of us.
"And that asshole said he would call me!"
Email is the circulatory system of getting shit done. When Twitter and Tumblr ideas escalate to actually happening, or Facebook users realize that they'd actually rather work than see one more piece of PlaceVilling proof that their friends are morons, people turn to the "To" field. There are still a few companies that email you a form and tell you to fax it back, but they're like a racist great-aunt complaining about the nursing home staff. You just nod and put up with it and wait for them to die. (If you really have to deal with such idiots, FaxZero lets you turn emails into faxes for free.)
"Hmm, this fax says we're running low on quills, leeches, and crude loincloths cut from the hide of saber-tooth tigers."
Email is like your mouth: You can use it to give very special attention to one person, or communicate with a group, but some people insist on vomiting all over the entire world. They put their entire address book into the CC field because this list of ten thousand jokes about cute kittens who found Jesus is the one that will make them less alone. Using CC instead of BCC is the email equivalent of unprotected sex, but much less fun. Now anyone can inject horrible things into the entire group.
Don't be sorry, BCC. (Guest starring the Invisible Man)
The address book CC is the mating call of the asshole with nothing better to do. It triggers an electronic Katamari of idiocy, rolling up a horde of Re:Re:Re:Repeats of the initial crime as morons reply to the entire group instead of the sender. Each reply wastes everyone's time. Especially since the "new email" icon on phones is now a Pavlovian response.
"It's not squirting MUCH, just hold it till I check my mail!"
There's no excuse for it. Any email program not programmed in stone has "Reply" as the default instead of "Reply All" anyway. You have to purposely choose the second option, a conscious decision to join the ranks of digital dickheads. A parade crowned by the king of the assholes, the one who replies all to scream "STOP REPLYING ALL!" Because they're too lazy to isolate the responsible parties or avoid becoming everything they hate.
Forums: The Asshole Turbocharger
The other assholes on this list evolved to infest new environments, but the worst thing evolution can throw up is an old enemy in a new form. The Internet is incubating some serious problems based on sicknesses we've already beaten. A great example of this is the anti-vaccine morons.
Patient Zero. Also IQ zero, medical qualifications zero.
Specialized forums install methane-induction compressors in the lower colon, because they're turbochargers for assholes. They're saving whole species of douchebag from extinction. Stormfront weaklings, misogynist cowards, anti-vax reversals of evolution, and homophobic failures now spend their spare time constantly reassuring each other that they're all right. Normally the social Brownian motion of interacting with other people would smooth off their rougher edges, or at least force them to keep quiet about them. But now they've uploaded their sense of community to a forum where everyone has the exact same problem. Instead of using the Internet to learn, they're carving out these asshole amplification chambers and marching out into the world louder than ever.
Good thing they banned swastikas. Otherwise the place might look bad.
Luckily, the solution to these problems is laughably simple. Laugh at these people, because they're simple. Explain how they're wrong, because it's important to stand against idiocy. Then refuse to get into an argument, because online screaming matches are just wasted time and hatred, and their entire lives have been spent training in exactly that.
Then use the most amazing information system ever made properly. Meet new people, find amazing things, and learn as much as you can. For example: MIT is now offering all its course materials for free. You could start learning aeronautics, neuropyschology, metaphysics, or any of a hundred other subjects, right now, for free. Or you could sit on your ass and refresh Facebook for another half hour. Go!
Because history teaches us that there are two types of people: the ones who use new tools, and the ones anthropologists dig up later.
Luke also looks at The 6 Worst Inspirational Posters Ever Made by Man, and probed the limits of an online asshole by taking The Donald Trump Endurance Challenge. Luke has a Tumblr and responds to every single tweet.
For more online assholery, check out The Cheater's Guide to Winning Online Arguments or The 7 Most Elaborate Dick Moves in Online Gaming History.