The problem isn't the game. The problem is that the players in question don't know when or how to curb their conversation regarding it.
An MMO is a shared experience. It's the same as two people who work together talking about work in their off-hours. Since they spend so much time together, they know all the same people, all the same drama, etc.
I have a friend who throws Poker Nights at his house, and invariably a lot of the people who show up used to work together at the same company. The conversation can't help but turn toward people they knew (and hated) at work, workplace drama, etc.
An MMO is the same. People who play often spend a lot of time online "together." They know the same people. They experience the same environment, participate in the same tasks, etc. etc. So when they get together in a social setting, they're naturally going to chat about their common experiences.
Out of our eight-person gaming group (1 DM + 7 players) four of us play
City of Heroes. Naturally, we are sometimes inclined to talk about the game that we all share. To bitch about bad pick-up groups, to extoll the virtues of particular powers, or the excellent writing of certain missions, etc. etc.
Courteous individuals will reign in that kind of discussion among mixed company, knowing that those not playing will not find it interesting and be unable to participate in the conversation. But should that not happen, it's certainly not the fault of the game. It's no different than any other shared experience that people can't shut up about in mixed company.