Simply, stop being dicks to each other. Politically motivated or not, a lot of people are just straight up cunts when someone says something that they don't disagree with.
I can forgive the political extremism, and being heavily biased towards Linux, but you don't need to insult anyone that's to the right of Bernie, or someone that uses Windows and is happy.
Lemmy is small enough that it cannot afford to alienate people, or afford to have a superiority complex over the likes of Reddit or Twitter. The best advert is to be a welcoming community.