the principles of free speech do not guarantee you a platform upon which to spread hatred. They do not give you the right to force others to serve your positions over the internet.
there might be something to be said about "platform neutrality," but it's still a competition of rights that doesn't really justify forcing a platform—especially a small platform like kbin—to host content it views as extremist, or especially likely to result in violence. Maybe you can argue that we should have higher scrutiny in the case of a monopoly or similar large social network due to the power of strong network effects, but... I don't know how much scrutiny would you need to apply to say "aha, this company is banning terfs for insidious reasons!" no, they're obviously banning terfs because their bigotry is dangerous and hurtful and giving them a platform just feels incredibly shitty.
A while back, I thought—well, I still do think—that platform neutrality should be used to frame the issue of large social media sites that ban talk about their competitors, like when Twitter deprioritized Substack (facebook messenger has banned competitors as well). I'd also argue this principle could be used to ban, for example, Facebook from manipulating its algorithm overtly (expliciltly, specifically) to favor a particular political party or an advertiser (outside of the ad itself—that one is already illegal, ads need to be disclosed as ads). But applying such a rule to general political standards and where you think the norm or neutral position should be is dangerous and stupid.