the platform becomes a biased support group

I completely understand what you're saying (and I haven't given any specific names because I'm not trying to shame anybody), except for this bit. I mean, I understand that it's common to think of supporting people in these terms, but I disagree that such behavior constitutes "support."

You're saying you disagree, but you're actually making the same point I did. The whole sentence I wrote was "people's flawed or even damaging interpretations get validated, because there's no opposition, and now the platform becomes a biased support group and not a discussion group." A 'biased support group; is not a good thing. You're repeating my point in bold below:

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If somebody really does see everything through that sort of lens, for whatever reason, actually supporting them should involve challenging perceptions that don't align with reality.

Otherwise, what you're really doing is reinforcing (and building upon) beliefs that do harm—both to those who hold them and those they accuse. It builds an environment where one believes that virtually everyone is evil and hates them, if I may use a bit of hyperbole.

Just saying, "it's perfectly valid to feel this way," doesn't help anyone, if it isn't actually valid.