For the same reason groups and corporations don't have voting rights, they shouldn't be able to monopolize speech by drowning out all others.
Additionally, money is not speech. We disallow politicians directly giving people money to vote for them - why would we do that, since the politicians trade is in speech, he's simply delivering stump speech in the form of a $100 bill to his potential constituents.
Money is not speech, but speaking publicly on a scale larger than a literal soap box on a street corner has never been free. Banning spending money to express oneself is banning expression just like banning paying for raw milk is banning raw milk.
And groups do have voting rights. That's how Congress works. The U.S. is a republic.
I'm saying that republics are voting as groups. By definition.
Not any arbitrary group gets to directly vote, no. But different groups do have rights: races, religions, genders, ethnicities, and, yes, groups of people with common values and interests.
Additionally, money is not speech. We disallow politicians directly giving people money to vote for them - why would we do that, since the politicians trade is in speech, he's simply delivering stump speech in the form of a $100 bill to his potential constituents.