Unions, like other monopolies, are good for their members and bad for everyone else. Whether unionizing is unselfish or not is debatable, but it makes the world worse.
Labor unions gave us the 8 hour workday, overtime pay, child labor bans, workplace safety standards, and union shops generally earn 10-15% more than their non-union counterparts.
ie Blizzard's CWA - it's scary to think about for many workers, so most people didn't bother to look up the details.