Online left-wing infighting seems to me to be about applying labels to people because they argue or have argued one thing on a particular topic, and then use it to discredit an unrelated argument topic or paint their overall character. I know there are pot-stirring trolls and compulsive contrarians, but I do witness users I personally judge to have genuine convictions do this amongst each other.
Within US politics, CA Gov. Newsom is an illustrative example (plenty of examples exist too for other countries and around Lemmy/Fedi). I don't particularly like him, he has done things I think are good, some things I think are funny, something things I think are bad and some things I think are downright horrible. Yet I have encountered some users online who will say they can't ever applaud a move of his if one specific other policy or set of other unrelated policies crossed a line for them. I'm not asking people to change their mind on what they think of a person because of an isolated good thing they do, but to at least acknowledge it as a good thing or add nuance describing what about it you like or don't. I can accept saying "I don't think this is a good thing in this circumstance", "this person will not follow through with this thing I think is good thing because ___", or "they are doing a good thing for wrong and selfish reasons" too. But to outright deny any support for an action because of a wildly extrapolated character judgement of the person doing it, when that user would support it otherwise, vexes me greatly.
I know this is not every or most interactions on Lemmy, but these are just some thoughts I have to get out of my head. You don't have to agree with me. I'm using 'left-wing' because the definition of 'leftist' or 'liberal' is wide-ranging depending on who you talk to. And on the side of the spectrum I'm calling left to left-centre, we seem to let the fewer things we disagree with get in the way of the many more things we would agree with each other. That's all, thanks for reading.
I'm not particularly experienced in online moderation, especially in managing serious issues in those spaces, so I would have to ask a friend about it, though I think the space she manages has different rules to her own views from what she has said. I doubt that the same issues that I am talking about occur as frequently though. The internet is much more anonymous and its full of trolls. I actually think its much harder to cultivate a culture online. I don't really think that anyone is actively changing their mind through anonymous online discussion. The idea of that being a thing was part of an astroturfing campaign to normalise shitty views.
IRL, I work with others from all over the left and I tend to be someone who is responsible for the emotional labour of accountability. You can't physically completely ban people from a scene without convincing as many people as possible not to hang out with them. You can ban them from chats easily enough, but people will cause a stink if you don't "use proper channels" and the worst predators will still show up to events anyway. Most of the time garden variety bigotry doesn't become enough of an issue to do that. Usually that only becomes an issue when someone starts hounding marginalised people and/or attending far-right events. People will often confront each other over bigotry before whisper networks develop but imo gossip is a really healthy way of keeping check.
What I mean is that prioritizing reducing infighting means that people within a community aren't familiar with raising issues, which means speaking out isn't normalized. It replicates the patriarchy on a smaller scale.