When our nation was established, the founding fathers had many examples to draw up upon to inspire the separation of church and state. In many governments past, the church and state were inextricably intertwined. The state couldn’t do anything without consulting the church, whatever church that may have been. The church held an immense position of power in society. This made it especially rough if you weren’t a member of the church.
The founding fathers recognized that this was part of the reason our nation was created, to escape the religious persecution of a state backed church. Some of the original colonists settled here primarily because of this. They were persecuted in their homeland and wished for a new life. They felt people should be free to worship how they choose without the state deciding for them.
The church controlled so many aspects of government, they would persecute those not a member of its ranks. A democracy obviously cannot survive perpetually if there is an entity that exerts that much control over the government. The amount of influence left for the voting citizens would consequently be greatly diminished.
In our day and age, we have a new church. It is called lobbying, campaign financing, and other non majority existential influences on government. These exert an incredible amount of control over our government.
The amount of anecdotal evidence is staggering, but on the edge of deniability because of its legal status. Those defending these practices hide behind the weak moral argument that they are legal. If an individual uses the code of law for their moral guidance then they are much worse off than many. If the majority believe something is wrong, even if it’s legal, then it obviously shouldn’t be legal; For what is legality but a codification of our collective moral compass in an attempt to preserve social stability?
Regardless the moral argument , the amount of influence these entities exert on the government is influence that cannot be exerted by the voting public. Thus if we wish to maximize the amount of influence the voting public has and stay true to the ideal of democracy, we must seek to limit the influences of these individuals and organizations in government.
Addendum: In addition to the church, the founding fathers recognized the threat foreign entities posed to the sovereignty of our nation. This is along the same line as the church insofar as that they both consume influence of the government that is then not available for the people. This is true regardless of the source of the entity, be it religious, foreign, or a group of citizens. We must protect the populace’ influence on the government from any entity who wishes to deny that influence.