If it was horseshoe theory they meant to discuss there would have been no need for them to say "This is classic far left". They would have said "This is classic extremism".

I'm not sure how valid horseshoe theory is in the first place.

This started as an edit to my comment but became more a comment of it's own:

Edit: I think you may be edited your comment? The bit you added sounds like a reasonable assessment, that anyone more extreme in their beliefs is more prone to manipulation, likely due to the fact their desire for change may override "common sense" as we might call it.