Any organization that centralizes power will become a target for others (individuals or orgs) to leverage/abuse that power. This is not limited to unions. We have centuries of laws and evolution of governance models to address known threats. The certainty of new threats is insufficient reason to abandon organized cooperation, because we can develop new defenses.

e.g. how about decentralization into smaller, independent, labor organizations focused on local issues, which build on open-source legal artifacts for governance, negotiations, threats and defenses?