While I don't disagree with this video, it kinda misses the point or rather seems to only consider the strawman of a person advocating for unquestioned "leftist unity". Which to be honest I have not seen in the "wild" (online or offline).
However what I have seen in the "wild" (but more online) are people that seem to spend more effort and time on fighting against other people that are broadly advocating for the same idea than actually doing something for said idea and fighting against real enemies of that idea.