Why should voters be protected against unlimited free speech for corporations?

To protect voters is a form of paternalism. Who is it who protects them? How do we know the protection is unbiased?

Isn’t paternalism condescending? If we say voters need protection, aren’t we saying they are too stupid to protect themselves? Aren’t we saying they can’t be trusted to make good decisions for themselves? Doesn’t that mean we think we know better (whoever “we” is)?

And what is the difference between individuals, groups of individuals, and groups of individuals organized under a “corporate” umbrella? How can we distinguish between the will of a voluntary group individuals who legitimately all support the same cause, and a group that voluntarily invests in an organization that is pursuing its economic advantage under the direction of its leadership?