When you look at social security, medicare, medicaid, minimum wage, the 8 hour working day, right to vote, and so much more, unions played an integral role in their development. There was a time last century when children were working long hours in fields, seniors having worked all their lives were living in poverty, and conditions in factories were like a "sweat shop". But workers fought their right to assemble and demand better.
I think it is easy in political sound bites to make it sound like unions are all bad. But when you have 400 people in this country making the same amount as the bottom 150,000,000 (about half), it seems clear there are some imbalances going on. The middle class has seen their opportunities and wealth taken away. Why would we then want to give even more tax breaks to businesses and the super wealthy?
If you have the time and courage, listen to Bernie Sanders give his view.