Not just “leftists and antiwar activists”.
Also all the people on the “right”, and libertarians and others who don’t fit into the “left/right” paradigm, who voted for or supported Trump to be the “bull in the China shop” against the “Deep State/Establishment”.
I’ve seen some of them on RT, although recently there seems to be more leftist opinion there.
But then, libertarians and Conservatives do have their own outlets. As well as (possible) false-flag operations.
I’m guessing the divide on the left between the “Deep State/anti-Trump Democrats” and the “progressive Democrats” more concerned with things like Syria (and WWIII, I suppose) is much newer, the wounds still fresh, than on the “Right”.
And, of course, we mustn’t forget that many of the “alternative” left-wing sources are funded by the same interlocking group of “elites” that control the mainstream media.
When the money-masters start pulling the chains, the formerly left-wing semi-established “alternative left” sites suddenly start sounding just like the Atlantic, right down to calling anybody who questions their sudden establishment shtick of being “fascists” or “Russian bots”.