He's more addressing the failures of left wing movements that he sees as arising from a tendency to seek out The One True and Perfect Ideology and assume that when that is reached suddenly everyone will be on board and revolution will happen, when in reality people will always have disagreements, and a perfectly unified movement is a dead movement that has stopped evolving (I'm doing a lot of interpreting tbh, he doesn't phrase it that way, but that's what I got out of it)

I think his point is that yes obviously you need to be aligned enough to have common goals and work towards them in a relatively unified way, but you can't expect to get everyone on the exact same page about your entire body of thought. Dividing lines should be drawn on practical lines, not on lines of ideological purity, because if you cut out everyone who has a disagreement, you will end up with a group too small to be a meaningful political actor (but obviously, some people will never join you or will work with you in bad faith and undermine your goals, sometimes the question is existential and a split or purge is unavoidable, but usually it isn't)

Some anarchists kind of have this tendency as well though it expresses differently. where there's this feeling that you can reach a consensus on everything, when you just can't, and it isn't required to take action.