You said it yourself that it hasn't been BAD ENOUGH that a rule need be enforced. This implies that speaking anything but English is WRONG, and that if it reaches a certain boiling point, rules to the effect of "speak English or gtfo" would need to be implemented to bring the "problem" back under control.
That is ethnocentrism, whether you are willing to admit it or not. But don't worry, the colonial empires of the nineteenth and twentieth centuries didn't know that they were being ethnocentric either. And your attitude that you are willing to tolerate it to a certain extent is elitism. Thus: ethnocentric elitism.
Who decided that English was the official language of the world? It's not, it's an unofficial lingua franca. And enjoy it, because 30 years from now, you may not be able to use map chat in Guild Wars 8 unless you speak Chinese.
I'll repeat that I'm not a native English-speaker; I'm a Finn and proud of both my language and my country, and am member of a Finnish-speaking kinship in both my MMOs.
If you think the attitude of the majority of English-only-proponents is "English or gtfo", then that's probably where this neverending argument stems from. I (we?) really, REALLY don't mean that, in any shape, form or subtext. I'm quite happy with there being non-English-speakers such as some (well, one) of my former guildmates in the game. But I (we?) think everyone should extend each other the courtesy of speaking in a way that the majority of listeners understands, whenever possible.
And yes, if everyone were to speak their native language on a multicultural server, it would be a problem. For the same reason it is a problem if everyone mainly speaks their native language at a multicultural workplace. The community fragmenting into nationality-cliques would be a bad thing and make the game less enjoyable for all. But as I said, I have not seen this happening anywhere, though I have heard hearsay. At that point the game would have a major problem in their hands, and I would not rule out rules as a potential solution; a bad one, but at that point I couldn't imagine there being a good one. In any case that's a very distant, extreme, hypothetical situation.
If 30 years from now we're playing a game that is in Chinese, and Chinese is the language that the overwhelming majority of the players understands, then yes I believe it would be rude to not speak Chinese in public in that game either, whever possible.
"Speak english or stop playing your stupid idiot" is quite common.
Then those prople are idiots, and that attitude is a problem, I agree. I have not seen it happen myself, and would dare say that most English-only-proponents are nothing like that. If your experience is different, then we will have to agree to disagree. However, even if the majority of English-only-proponents were morons, it would not detract from the point of why people think speaking non-English languages on widespread public channels is rude.