The sectarianism and people aligning strongly with different primary candidates will always be a thing. Acting like everyone but Bernie supporters were being polite isn't realistic. It wasn't right for some of them to get really nasty but they were also constantly getting crapped on.

It'll continue being an issue due to the party system and especially since our messed up political system is built around 2 parties. We can unite more during the general elections but in between that time, it's more contentious with various people to the left of Republicans who have very different views and different politicians they support.

The threads on this sub vary a lot. Sometimes it seems like mostly people left of Democrats who are as critical of them as Republicans or even more so, sometimes more people who support the party. It was never meant to be a sub for a specific political wing, the content is determined by who is participating the most at a given time. I recommend the overtly Democratic Party align subs more overtly pro-Democrat if you rather see less comments from those left of Democrats, though those subs will be less active than this one.