Actually, a corporation is an entity empowered by law to do certain things (e.g., shield its owners from personal liability) that a mere aggregation of people cannot do. The Supreme Court majority in the Citizens United case missed this important distinction.

I think it’s possible to draw logical and constitutional lines between

¶ 100 people writing letters to their Congresscritters advocating for the same policy

¶ a manager of a corporation (with 100 shareholders) writing Congresscritters to advocate for some policy (that not all 100 shareholders think is a good idea)

¶ a corporation hiring a lobbyist to be its permanent advocate in Washington