Dollars are Free Speech and Corporations are People

Take a labor union that represents a thousand workers. The owner of the company they work for decides to support an anti-union candidate. She can only donate a few thousand dollars to the campaign, but she can independently spend ten million dollars advertising how great the candidate is because the 1st amendment says the government can't limit her personal political expression. The union doesn't have the protections of the 1st amendment, so it can't run a counter-campaign against her. Each individual has to run a thousand different campaigns.

Buying a billboard is your personal right. Citizens United says that right doesn't disappear when a group bands together. This in theory helps the common man since otherwise the wealthy are the only ones who can afford to run a parallel campaign.

The problem we are facing has nothing to do with that. Our problem is that wealth inequality has gotten so bad that the rich can drown out the collective voice of everyone else. The rich were already figuring this out before that decision.