Unionizing is only antagonistic if you think management really does want to screw over workers. In a healthy workplace, the union absolutely wants the business to succeed and profit, so that the workers can also benefit. Unions are a way of representing one of the competing interests that you identify.
This is often (though not always) true for single-company unions, but not for unions made up of employees at multiple, competing companies. The game theory gets complicated when you're using one negotiation as leverage or signalling for your next negotiation at a competing firm.
