This is where I agree with the Libertarians. Every time you try to overturn Citizens United without gutting the 1st amendment, you find yourself going down a rabbit-hole that gets curioser and curioser until you find it's just unworkable.

It's not the money that's the problem, it's the actual quid pro quo and the revolving door. It seems like there ought to be ways to bar people from positions and/or seats on the boards of corporations without violating fundamental rights of free association and expression.

Also, if corporations were not "persons", this wouldn't be a problem either since you can violate the rights of a non-person all you want. OTOH, when you form an organization for the express purpose of lobbying, that's free association and expression. You have to allow it. IMHO, I think we could bar Grocery Store, Inc. from making contributions without trashing the 1st amendment, but not AARP. That makes sense to me because joining AARP is optional; but buying groceries isn't. Likewise, if you must join a union to do your job then that union should be barred from making donations; but if union membership is optional then fine--let them donate all they want.