The mantra of "greedy teacher unions" or "greedy unions" or "greedy overpaid government workers" appears in letters to the editor, blogs, and even in articles by people who should be more objective. These phrases have the same nebulousness as "paying fair share". "Fair share" generally means "more" but little thought goes into why some should pay more taxes.
"Greedy unions" generally comes from those who not only don't want to pay more taxes, but they don't want to pay more wages to their employees. And guess what they form to advance their agenda? Unions!
They aren't called unions, but they are in the sense of coming together to advance an agenda. These include Chambers of Commerce, American Legislative Exchange Council (ALEC), numerous "conservative" think tanks, and many, many trade associations.
Like every other group, they work more to advance their short-term interests than to advance the public good. They want government off the "people's backs", but then they rush to government for contracts or laws favoring one industry over another.
Like every other group, they purport to represent all like them. As the Occupy movement claims to represent the 99%, these CEO unions claim to represent all businesses. But the large corporations do not all have the same interests, and the large corporations do not have the same interests as smaller businesses. McDonald's does not represent the interests of all restaurants, and Walgreen's does not represent the interests of all pharmacies.
Organizing to promote a special interest is the American Way. It was going on before the ink was dry on the Constitution. We just have to be vigilant in our reading to look for hidden agendas and slogans over careful thought. It's a hard job being a good citizen and voter.