Playing happily on Amerish during an intense firefight in a forest I get a side hit, move around a big tree to get some cover, then get a second side hit (WTF - how many snipers out there?), move again, looking around but I only see a friendly close by ... Move to yet another tree, the friendly is still following but I get a third and a final fourth hit - dead. Then the death screen appears and I can see I am victim of a blue-on-blue accident, friendly XXX killed me. Then I recognize the name, it is the same guy who was following me and then I see another message: "The invitation of XXX to join his squad had expired" and I understand ... So this guy invited me to join his squad and was so pissed out I didn't that he decided to chase and TK out of rage? What's the average age of a PS2 player? 12?
I dont think age is the factor as much as emotional maturity, the lack of accountability and anonymity that a mmo provides. These factors contribute to the terrible behaviors that a small percentage of players display. Team killing and 4th faction shenanigans included.
Which still makes them children, one way or the other. They could be 50, and I'd still call them a child for behaving like this.
Immaturity is a likely cause as it manifests as self righteous behaviour and self justification of rule breaking, amongst other things. I always report - DBG policy is not to give feedback so you never know. But they can't act if you don't tell them. I recently decided I would put a bounty on deliberate TKers as well but no one has blatantly TKed me deliberately since then so I haven't tried that (don't even know if you can bounty one of your own faction tbh).