The original point about Antifa was sound. Antifa is to anti-facism as the Patriot Act was to Patriotism.
As far as BLM goes, there is a very clear statement of belief on the website.
https://blacklivesmatter.com/what-we-believe/
Most of it is pretty straightforward and focused on, well, black lives mattering. There is some far-left identitarian bull#### mixed in there, but for the most part, the extraneous stuff that BoLevi attributed to BLM isn't actually there.
There are certainly BLM leaders who hold and express views about topics outside of what BLM says its mission statement is, but that's not surprising, as there's no expectation that if you sign on to be a BLM leader you're not allowed to have views on other political topics. There might be an argument that BLM as an organization should do a better job of avoiding the pollution of its message by its supporters but that's a different thing than suggesting that it's cloaking more controversial ulterior motives in an uncontroversial central position.