Ah, so there it is.
If only individual people are allowed these rights then newspaper editorial boards cannot endorse a candidate. Political parties as we know them are now defunct as well. Who gave them the power to speak in endorsement for the people? Does the DNC or RNC only get to speak if their chosen person won 100% of the primary vote?
Or do you mean to say that some corporations are special while others are not?
Although with that last statement I must somewhat agree with your point for unions. Some people who have their money taken have no say in the matter due to the work rules in some places, so that is unfair.
To say that an assemblage of people cannot pool their resources for speech borders on the absurd. To say that by filing the papers they have created an extra person is distorting the matter. A group of people assembled in common cause has the right to speak otherwise the very notion of assemblage is meaningless. One voice can be powerful, but a group with the same goal is much more powerful. Look at the Tea Party or OWS. What is the difference between these groups and the corporations? All have a vested interest in the politics and governance of the nation. All are collections of people, that may or may not agree with every single issue, but yet the larger bodies have the ability to speak, to spread their ideas, their goals. If someone does not like what the collective is saying they can leave it and disavow membership and then go about their business.
As far as speech backed by dollars, all speech is backed by dollars. As in everything the time I can take to rail on about an issue depends on my ability to pay for the needs to do so. Whether that is the food and drink to survive, the cardboard to write my message on, the computer and internet access to spread my message across the world, the printing press to make pamphlets, or the access to the radio spectrum to get my voice and image out to the people.
The question you seem to be asking is should groups who pool their resources and create much deeper pockets than any one person can be allowed to use that money for political speech. The answer has to be yes, because to deny that to one group creates an environment where some assemblies of people are more deserving of rights than others. What walks on four legs cannot be better than walks on two legs just because we say it is so.