Once again that's IMHO an oversimplification, the problem is not really in condemning racism, homophobia, whatever... the problem is that, over the years, those words have been so abused and overused that they lost a lot of their meanings.
Nowadays they are thrown around so easily as soon as somebody feel "offended" or even as soon as there is any sort of disagreement, regardless of whenever or not they are actually justified, so it's no surprise that some start to consider those words as being meaningless buzzwords, or even "name calling".
I don't think that many peoples are "worried" that hate speech, abuse, outright racism, etc... end up being forbidden / restricted on this forum, no, but some peoples are worried that some others starts calling racist, sexists, etc... anything they don't like and try to abuse of the forum moderation rules (if those are too "blurry") to remove anything that doesn't perfectly align with their own personal agenda.
And no, I disagree that they "have" to alienate peoples, if there are clear "neutral" rules, that the moderators judge posters / posts fairly based on those rules and not on based on their own belief. I think that it's possible to have peoples of various political alignment frequent the forum have have discussions without anybody (apart from the most extremist on both side) needing to feel "alienated".
It won't be easy and there will be peoples warned/banned, thread closed, etc... but it's possible.
That's one subjective impression. With a lot of implicit premises, of the very commonplace "i am reasonable therefore those who are far from me are extremists" sort. The kind of premise which justify the just as widespread "racism is what others believe in, therefore what I believe in is devoid of racism".
There is a whole spectrum of standards, about racist mindsets, depending on various subcultures that are all represented on a gaming forum. It goes from the relatively rare, proudly admitted racism, to the continuum of much more common denied racisms ("i am not racist, as we know it is a bad word, BUT..."), to naive antiracism that are very ambiguous and patronizing ("noble savage" phantasies, clumsy well-meaning feel-good movies, etc), to all the ambiguities of academic research (explicitely antiracist but still permeated by subtle ethnocentrisms), etc... These are all very different degrees. But you could still split it all into three broad areas : embraced racism, denied racism, aware and reluctant racism. And these levels come with very different levels of self-awareness and attitudes.
The further you go to the academic world, that is, into the most rigorous and self-reflexive domains of research, the less is "forgiven", because the less can be afforded. In anthropology, the most specialized field of knowledge about cultural differences, there is a strong awareness of the unavoidable ethnocentrism (and the pitfalls of culturalism and essentialisms) that can very subtly distort researches on the unfamiliar. Dealing with this awareness is part of the methodology. Nobody considers themselves exempt of these biases, but what matters is the effort to overcome them and get as accurate as possible. So, keeping an eye for them, and pointing at them wherever they manifest themselves, no matter how subtly, is central to the methodology. Just like surgeons take care about disinfection, or astronomers about lens surfaces, programmers about sloppy syntax, etc.
Politics, infotainment and common sense discourses, have a very different approach to it, as racist reflexes are very fruitfully instrumentalized (and re-branded) by rhetoricians, to varying degrees. This is horrifying by academic standards. But as society evolves, it incorporates more and more of the popularized scientific knowledge. And society does evolve, as we've mostly left behind a series of outdated conceptions of the humans (such as the racialism that was justifying slavery, the sexism that was excluding women from politics, etc). It doesn't evolve uniformly. Each progression has met cultural resistance. Each traditional worldview has fought against its marginalization. And, at every moment of history, society has been stretched from the reactionary pole ("let's go back to former beliefs"), to conservative norms ("we have reached perfection, because we are us"), to the most progressive poles ("let's not be too self-satisfied, look at all there is to yet ameliorate"). In terms of societal beliefs, you can see both this evolution and the differencial of attitudes about it in mainstream fictions : a smaller part of the public manages to enjoy unironically the (now) blatant sexism, racism, and homophobia of older movies. A small part of the public is sarcastic about the (still) latent sexism, racism and homophobia of our current productions.
So, claiming that there is an objective "middle ground", threatened by the respective "extremism" of reactionaries and progressives, is itself a very situated conservative point of view. Reactionaries will complain about the "politically correct" oppression of racism, and progressists will grow impatient about the mainstream conservatives still being naively unaware of our current shortcomings and ethnocentered assumptions (and the way re uncritically reproduce them in public discourses). This has little to do with any objective notion of "extremism" as opposed to some noble (temporary yet imagined intemporally valuable) "middle ground".
GOG's conundrum, right now, is to deal with this spectrum of standards. This means, defining a line of acceptability somewhere in that continuum. There is enough of a social consensus about the reactionary fringe's overt fascism (Infinity9 regretting the end of segregation and praising Pinochet, Kingsbradley campaigning more or less overtly for the neonazi Golden Dawn, etc), so this will certainly go. Then, there is the ordinary spectrum of "I am not racist but", which is more complex to deal with, because it is quite diverse. Not only diverse in terms of intensity (going from parliamentary far-right militantism to ordinary ignorant common sense) but also diverse in their objects (for those who really don't care about introspective discipline, racism is very visible when it's about human groups very remote from their own everyday concerns, but suddenly very justified -and nonracist- when about human groups deshumanized by their own daily newspaper). The acceptability threshold will be awkward, especially when the speaker adheres to this commonplace denial of ethnocentric biases (which is the surest way to never have them addressed) yet strongly agrees that they would be A Bad Thing (hence the outrage of being accused of it). In contrast, the most progressive people usually welcome a heads-up when being signified of such a bias having crept up. Because they already know that it is a constant issue, which gravity depends merely on the intensity and the good will or bad will behind it.
So, no "neutral" ground there. The only actual "neutral" position would be, objectively, way beyond what you'd consider as extremism : it's the cognitively unreachable state of freedom from ignorance and ethnocentrism, and not even the most trained, seasoned, veteran anthropologist could claim it. And we would probably all fail to match it, because we're humans, with all the cognitive limitations it implies. What you'd call "neutral" would be simply a temporary social consensus, based around some statistical average of awareness in your own society, or, more likely, your own speciific subculture within it.
And what will certainly happen instead, is a norm set around Fable22's (or GOG staff's) own subculture, with some margin of tolerance. It won't be academic standards, it won't be neonazi standards either. We do all cross our fingers for these norms to be within acceptable reach of our own respective ones, but the way we all imagine ourselves as The Neutral Point of Reference is utterly naive. Let's simply hope for a good comprimise between objective decency and realistic (international early 21st century) expectations.