On the whole I lean towards being anti-union. I've always worked in the private sector so if my employer decides to make redundancies then tough s***. While I appreciate that unions can help people have rights, I do think they go too far in many instances - e.g. the transport unions in Europe are f***ed because they won't accept that modern trains don't need as many people to run them, so the unions are always striking when cuts are proposed.
IMO union strikes shouldn't be allowed for public services like emergency services and transport.
Specifically in baseball, a union for umpires just creates a cartel. It's unnecessary and discourages advances that would help the game (like video tech, and sacking Angel Hernandez).