I don't have any stats on what % of twitter is bots so I'm not saying that it's not overwhelmed by bots, but we should be aware that there might be an even more chilling explanation here: that it actually _is_ humans causing the toxicity
But I've also come to roughly the same conclusion as you. I might be naive, but given the time I've spent on the internet, I'd like to think I can tell the difference between bots and humans. Some of the bots are obvious, some of the bots are non-obvious (blaming bots), but still definitely bots. But MOST of them, are probably real people. Really, really ignorant people, on all sides of the political spectrums. There's just these people out there now with phones and a Twitter account, and they're broadcasting their id.
Twitter is a pure pain box, but no one has the kindness of offering a gom jabbar.
Maybe this is an ML thing, though. The Twitter ML community is much tighter-knit.