Slate Star Codex wasn’t a nuanced conversation. It was a gathering place for people who wanted to discuss “scientific racism” without using those words or the other well know dogwhistles. It’s great that SSC stopped providing a platform for that.
I dunno. There may have been some commenters with those views, but from what I saw it was a tiny minority. And most discussions never touched on those sorts of topics at all. Are you sure you weren’t reading a different blog?