Nowhere does the Constitution of the United States mention corporations. Nowhere does the Declaration of Independence mention corporations. Corporations are not real people. They are legal fictions created by legislation to facilitate economic activity. The purposes for which a corporation may be created are defined by the statutes under which they are incorporated.
The Bill of Rights limits the ways in which the government can interfere with the activities of people in the United States. However, corporations have never been allowed to do anything that the legislature did not say they could do in the first place. No one can tell an individual that he may not pursue a lawful profession, but legislatures have often limited the extent to which particular professionals can do business as corporations. This is why law firms and accounting firms are typically organized as partnerships.
For more than a century, Congress has limited the extent to which corporations may participate in the political process. Many states legislatures have imposed similar restrictions. Since a corporation's right to engage in any activity is defined by statute, there should be no reason why its political activities should not be subject to legislative limitations.
In a brazen usurpation of legislative prerogatives, the Supreme Court of the United States has decided that
Congress cannot make such distinctions between corporations and real flesh and blood human beings. By such logic, corporations should be allowed to run for office and to vote.
Conservatives love to whine about activist judges who make laws rather than interpret laws. I hope they will make their voices heard now.