In the ruling, the SC made it expressly clear this was not some corporate pseudo-person's right to speech, but rather the rights of the owners, who carry along the right of free speech whatever they do, like anyone.
As AK Marc already pointed out, those owners already have their right of free speech, as individuals. Citizens United has conferred a further right, that other individuals do not have.
This was an attempt by right-wing extremists on the court attempting to extend the power of the ruling elite just a little longer. It will absolutely be overturned, and in the future, Citizens United will be looked at as an artifact of a shameful period in our history, sort of like Brown v Board.