Let me sum everything up : the Internet is not serious business. So don't take it seriously. It's not real life.

Well there's also growing out of that "phase", which does not necessarily ential violence or harsh social mis-haps.

tongue-in-cheek:
tb, have you considered you might be dealing with a higher percentage of jerks because of your vocation? I'd assume a good chunk of your customers are nerds, and not in the GOG Nerd sense, but the Ain't it Cool/4chan Nerd sense. I wouldn't be surprised if some of them were jerks in real life too. It makes sense you'd be "over exposed" to jerks like that, after all you work at a PC shop. Nothing else would get these guys to leave their mother's basements other than your store dedicated to the only thing they've ever made love to. ;-)
You just gotta think positive and remind yourself there are plenty of chill, respectful gamers out there-like us :-)

Read subject of conversation first before posting, the transition of this online attitude to real life is what I am talking about. That means when I do log off I still see this online attitude in big cities and small towns. Your solution is clear alright. Clearly didn't work because I log off and still hear things like "BRB" or get the actual attitude of people who bully their way through a conversation because they think nothing will happen to them as if they are online.

So, out of curiosity, does anything then proceed to happen to them when they do these things in real life? Basically, is this really something that's bleeding over from online behaviors, or is it a behavior that's born just as much from offline consequences (or the lack thereof) as from online consequences? Because as much as some folks like to play internet tough guy and talk about how if anyone said certain things to their face they'd beat up that person, people getting beat up for talking shit actually doesn't happen very much in the real world (not to say there aren't consequences, they're just not as drastic and obvious as some folks like to pretend they are).

Okay, fair enough. However, people bullying their way through conversations, or just being horrible conversationalists, isn't anything new. I don't really see how you can attribute problems like that to 'them damn kids and their leet talk'.
And why get so hung up on someone actually saying 'BRB'...it doesn't affect you. Roll your eyes at them, sure, but what ever. I just do not see why this is such a MASSIVE PROBLEM to you.

Indeed, It's just a new word/phrase. Those appear all the time. It's not any better or worse than any other new word. Live with it.

It's people 'living with it' that has allowed it get progressively worse and institutionalised. I am not advocating smacking people, but manners should still be expected and enforced. Unfortunately we live in an entropic universe, which always leads to decay. Rome became decadent and morally bankrupt before its fall, and we are going the same way.
Just my thoughts.

So true. I sympathize with him but he is taking it too far and acting just like them.

"Be careful when you fight the monsters, lest you become one.... and if you gaze for long into an abyss, the abyss gazes also into you."
He hates people from the Internet talking smack IRL... therefore - he becomes the Internet Tough Guy and talks smack about what he would do to THEM.
The irony is overwhelming.