And here's a comment to the article that I really appreciate:
Unions are largely responsible for the middle class, even if you aren't in one. Unions historically represented workers who individually had no bargaining power, typically people who are easily replaced. Without the power of collective bargaining those workers would never have achieved reasonable wages and benefits.
Even nonunion workers benefit from unions in a couple of ways. First, in industries where workers are known to unionize, employers have an incentive to keep them happy so they won't unionize. Second, higher wages and benefits for one segment of the workforce bleed over into other segments. You and union workers are both part of a larger workforce and what affects one finds ways to affect the other.