The chief issue with unions is that most of the major issues/battles with labor that unions were created to address and fight for have long been fought and won. Outside a few industries (most notably coal), unions have won all the major fights, to the point that everyone from Gen X onward have lived in a quasi-workers paradise and never experienced most of the crap that workers had to endure before the rise of the unions.Unions work in short bursts and should transform into a Watch Dog group after it's accomplished its first mission until a time it's needed again. As it stands it's just a second head to corporations trying to fight itself.
Much like anything that outlives its purpose it becomes corrupted from its ideal.
This in turn has create a sort of distaffed view of unions where the unions exist solely to justify their own existence and become machines of their own, sucking up union dues that rarely if ever are used to actually benefit the workers and only the upper/middle level union leadership who get paid more than the average worker. Worse, is the fact that unions have introduced their own kafka-esque hell of bureaucracy and corruption that allows incompetent workers to avoid being fired and the perverted form of "some animals are more equal than other animals" preferential treatment, that is a blight on the face of writers/creative type guilds.
And the later is the only reason the SJWs are pushing for a union: they want to pervert the comic industry the same way the movie industry was perverted and turned into the ultimate SJW only clubhouse that it was in the 1930s/1940s when Dalton Trumbo and company ran the Hollywood Writers Guild of America. Trumbo and his commie friends basically blackballed anyone who wasn't a screaming commie from gaining Writers Guild union membership, which was a huge thing because the Writers Guild Union had a contract with the major Hollywood studios that they could ONLY use WGOA writers. As such, only SJW Commies wrote for the major studies and even if you were a member, you could be denied plum writing gigs if you said or did something Trumbo and company disliked, like call out the mass murder committed by Stalin (as Trumbo was a huge Josef Stalin fanboy). It's one of the chief reasons WHY the Red Scare in Hollywood happened, as far as being used by the studios and conservatives in Hollywood to break the WGOA and free it from Trumbo and company's evil grip.
This is the only reason the lunatic left want a union in comics: to solidify their stranglehold over the Big Two and Indie comics and make them unfireable and ensure no conservative or moderates/sane lefties are ever allowed to work in the industry.