I'm not sure I entirely agree. Certainly, if you identify a specific case of "this person did this horrible thing, so he is a horrible person" and I use the "Well, not all of us are like that"... that is an useless statement. However, if you say "this person did this horrible thing, so all of you are horrible" then you have forced me into a defensive position where I must defend myself with the "Not all of us" argument.
Instead of defensively reframing the criticism as being about you (you being the global you) and others who aren't the problem, you can instead acknowledge the problematic people and condemn their words or actions, right?
"The Giant Bomb community is acting awfully."
"Well not all of us are, that's completely unfair to paint us all with a broad brush, it upsets me."
Vs.
"The Giant Bomb community is acting awfully."
"Yeah, some people are being assholes. I hope the rest of the community calls them out, we don't welcome that, and wish they'd leave. They're not welcome here."
These both impart that the larger community is not like this, but one does it without reframing the discussion about you (globally), and doesn't derail the discussion. One of those also better acknowledges the underlying issue as being an issue.
What would you suggest the majority does about this minority then? If you correct their ignorance you are just joining in the argument and prolonging it.
Also, what defines this GB community? Do you have to post on their forums to be tainted or are all fans of the site the "GB community". 'cause here you are posting in a GB fan thread. So what are you doing about people in your community?
Are you arguing people shouldn't be called out or corrected when they say something awful, ignorant, or discriminatory? Because the majority absolutely should do that if they don't want to implicitly allow it or have people think it represents them.
Personally, I'd consider myself in the community, and what I do is call out or question people who say awful things.