Maybe it's because white people have stifled those discussions for ages? For every white person that has something worthwhile to add to the discussion, there's usually a handful more there just to dismiss the problem because they have no perspective and it doesn't effect their lives personally.
I see that you're trying to point out a double standard here, but it's not really comparable when you factor in the centuries of oppression and everything.
I agree with this.
At the same time, for this specific discussion, depression and suicide are often mischaracterized as a sign of "weakness" and that perception leads to all kinds of issues. The biggest one being those most desperately in need of outside professional help not reaching out to get it. To come into a thread mostly dealing with mental illness and suicide, which I think are generally misunderstood by a large segment of the population to the detriment of those suffering, and to immediately jump into a discussion of white fragility can easily been seen as either insensitive or as far as NeoGAF goes, purposefully inflammatory. Not because it isn't a part of equation but because making it the focus of the discussion completely misses what should be the point.
Basically that topic, like many others, is one NeoGAF as a whole couldn't even begin to do any justice or give deeper insight into (a few posters probably could but most of the good ones don't waste their time) because it requires a deft touch and a base level of understanding they just don't fucking have.
I do agree there isn't a double standard here because I don't think the situations are similar. White folks clumsily whitesplaining racial issues to PoC or stumbling over themselves to handwave away institutional racism will always have a very different connotation for the reasons you've mentioned.