> Because when people say “avoid politics” they usually mean it as a derogatory term for “all the disagreements that I dont personally care about” - and conveniently exclude the issues they care about from “politics”.

People use "politics" as shorthand for "things that are divisive issues that split your purported represented class". You're not going to get anyone to join your union if all you do is advocate for things that the vast majority of employees at best don't care about, or worse, disagree with.