My brother in law asked me this exact question last year.
I told him mostly Twitter (which is sort of true but I didn't feel like getting into specifics), and he frowned and said something like, "it used to be good for that."
Edit: Then I replied telling him it's just a link sharing site and you can make it as left or right as you want to. But he wasn't having it. The CBC (he's Canadian) told him it's now a racist hellscape and so that's what he believes.
My brother in law asked me this exact question last year.
I told him mostly Twitter (which is sort of true but I didn't feel like getting into specifics), and he frowned and said something like, "it used to be good for that."