Michigan voting on "right to work", what is the controversy here?

[Jim in CT]

Curently in Michigan, many industries require you to belong to a union. You cannot work there unless you belong to the union.

They are likely to pass a "right-to-work" law, which makes union membership voluntary. Liberals are going berserk, and even Obama campaigned against the law while he was in Michigan.

Can someone please tell me, why anyone would oppose a law that gives me the right to choose whether or not to belong to a labor union? Unions are extremely political - they give huge $$ to Democrats and to liberal causes. Here in CT, my brother was a public schoolteacher. When he found out his union dues were going to Planned Parenthood, he successfully sued to get out of the union.

How can ayone support the notion that an employer can force employees to join an organization, whose stated goals you may be opposed to?

I'm sorry, I don't see the argument in favor of forced union membership. I get why unions are against it (they will lose membership dues). But what gives unions the right to force people to join and support them with dues?

Anyone?