However, your interpretation of Citizens United is off. In Citizens United, SCOTUS did not "establish corporations as individuals allowing them to contribute to political campaigns".
There's a much longer history of SCOTUS saying corporations have some, but not all, of the protections of the Bill of Rights. Citizens United basically reaffirmed that, but is nowhere near the first ruling to come that conclusion (contrary to popular belief).
Also, Citizens United was not about corporations donating to political campaigns. Generally speaking, it has to do with corporate political speech & how it is paid for.
Much thanks for the Citizens United clarification. But I am gratified to know that Citizens United is a growing crack in the progressive foundation and is being used in the Hobby Lobby case.