I agree, but I never dug enough to get these answers. I just noticed the pattern of behavior.
I think that the progressive discourse since the turn of the millennium did get increasingly preachy, to the point where even I, who am sympathetic to many of their pleas, find them annoying quite often.
Another friend I have hypothesizes that what is generally seen as "left" during that time frame moved on from class struggle and economic inequality (which used to be major talking points in the 80s and 90s) to more soft social issues. As a result, some of the lower classes started to embrace ideas of those that blamed others for their misfortune (be it immigrants, gays, blacks, etc). I find that an interesting argument, but never took the time to more thoroughly inspect it.