That's an interesting question. Can a community ever collectively hold an opinion? If I form a society which specifically states that its stance is that "blue-eyed people are superior to brown-eyed people", then that organisation could be meaningfully described as being prejudiced. If they act upon that, they could be described as discriminatory. But the community - that's the people in the society. There might (or might not) be some people in my society that don't share my opinion. Perhaps some misunderstood our motto, "blue good, brown bad". Perhaps some consider themselves to be infiltrators, trying to spy on us on behalf of the browns. Perhaps there are others who are in Blue Club because their parents, or their friends, or somebody they're attracted to is in it, and they don't actually agree with it. Perhaps some are members just because they like the people there, and not because they necessarily agree with the overarching politics. So I would say: Blue Club, the society - the one with the outwardly-stated opinion - is generalised. But the Blue Club members? Not so much. You might say, "our survey showed that all of the members of Blue Club, an organisation that claims that blue-eyed people are better, hold the opinion that blue eyed people are better than brown-eyed ones", because that explains the limitations of your measurement. But to say "all members of Blue Club are ocularist"; perhaps an overgeneralisation. And perhaps more-importantly: whether or not it's true that everybody in Blue Club agrees with me, it's still not-productive to attack them as individuals. Attack the policy, not the person. If we observe that Someplaceistan has laws that make it impossible for women to get jobs, or that make them "property" of men, then it's not fair to say that "all Someplaceistanis are sexist," or even "all Someplaceistani men are sexist". What we are disapproving of is the policies, not the people; and the sooner we can see the difference between the two, the sooner we can build bridges to understanding, rather than blowing them up.
Okay, I agree with that, particularly that we should attack policies, not people. I think there are cases where it is useful to generalize groups that don't have outwardly-stated ideologies (for example, when describing the political leanings of reporters for a given newspaper, or lobbyists' agendas) - with the critical distinction that these generalizations should not be done as a value judgments, but rather as observed trends of behavior for the purposes of rooting out possible effect of biases on information coming from those groups. In the case of reddit and sexism, therefore, I think it would be fair to say that language and behavior that objectifies women tends to be upvoted highly and given more weight by the community than criticism of such behavior, in at least the default subreddits.
Well-explained. It seems that you're saying that it's sometimes acceptable to infer policies and ideologies from the collective behaviour as a group. And on reflection, I agree. My real concern, I think, is that judgements like this, made from the outside, serve only to further polarise the behaviour. For example, describing Reddit as sexist, as an outsider, has the effect of removing Redditors who do not want to be considered sexist (probably because they're not), which in turn increases the net-sexism of the community. Labelling a community from the outside may help to shun them from wider society, but it doesn't help to fix them: that has to happen from within. (not that I know the best strategy to do that with Reddit and sexism, though, although I try to do my part to downvote/criticise/educate where appropriate)