Yeah well I wish I had a clear answer to the problem you're correctly identifying. Probably the best way to get around at least the first large chunk of issues, is focusing a lot on education. Quite frankly many liberal progressives, the good ones who would value more highly human emancipation and progress than clinging death-like to private property at the expense of all else, function largely based on enlightenment moralism such as a "categorical imperative", as well as are hardwired for dualism rather than dialectical materialism (for example.) IMO these out of date paradigms are woefully insufficient for the present task.

But even among like-minded individuals there are big problems to move beyond. I'm in a group of political activists that go to great lengths to vet its members. It takes a minimum of 4 months of study and discussion to be even considered to join, and activists had often been studying for years before and continue to study once accepted. The group was formed by some organizers who have been working together for decades before splitting from their old group. We are a very democratically run org, that works to influence mass movements and call for the creation of a workers party by and for the workers, in order to establish a worker state to transition to socialism away from capital and private property.

Long story short we have vicious disagreements despite our collective work, our shared education and frequent comradely discussions. The scope of what we disagree about is narrower, but the disagreements are almost irreconcilable. Personally I think some people could be more introspective, others better communicators, others less dogmatic. Various differences manifest as two distinct factions in conflict, with the rest of the membership left to tip-toe around it, or set up in one camp or the other. And this is a very good group! None of these critiques venture into the sort of interpersonal cattyness, or downright abusive behavior from leaders of other groups. We don't have those particular problems, but yet problems emerge nonetheless.

But moving into a more "repressive" period under trump might have the effect of unifying many peoples differences and burying different hatchets. Temporarily. Its a mistake to think that individual ideas or ideology is solely responsible for the difficulties of the left. We exist in a milieu that is hostile and confused, at least some of the hostility and confusion amongst us is part of that influence. Having an external "enemy" to struggle against has a way of unifying differences and replacing important priorities with urgent ones dictated by history. Also things can move very quickly once society reaches a tipping point. Objects in our predictable future may be close than they appear. I hope we can get our act together, and will keep working to try and make that real