Why does it go both ways? The symmetry isn’t obvious. I can kick you out of my house for whatever reason but I’m not automatically complicit if I let you visit and you pull out a rifle and shoot someone out the window when I wasn’t looking. That is right. And it should be that way.
My personal residence doesn't serve as a chosen communications venue for a significant fraction of the local populous. Network effects are real. Failing to consider them is specious.
That doesn't mean I'm necessarily in favor of preventing these companies from moderating things. It just concerns me to see such obvious aspects disregarded.