How do people pick a religion?
In the end, individuals decide mostly by their need for ethical guidance and spiritual renewal. The Catholic Church may have objected to Galileo’s argument that the sun is the center of the universe but the Protestant Reformation had already occurred. The imagined threats to the Church's authority and infallibility posed by science are minor compared to the ethical, political and spiritual needs of human life which are ultimately the drivers of religious practice in a culture.
How, then, does a religious-seeking person decide on a religion and/or denomination? How do you decide Jesus is right and not Mohammad? If you are going to reject Mohammad as a violent oppressive tyrant, do you not already know that such a model is an abomination? Thus, you have to know right from wrong before you decide which religion is just and respectable. This suggests that ethics can be known without religion and indeed it must if you are going to be able to avoid being trapped into a nefarious religion or cultish denomination. You don’t just follow Jim Jones to Guyana … you use your own mind and decide this guy is pure evil. You don’t just join the jihad … you use your own mind and decide this path is barbaric. But that means you need a standard to judge—an ethical standard. Ethical knowledge must come first.
I wonder if this is why some conservatives can’t be critical of Islam. They seem to believe that a long-standing widely-shared religion must have some truth as its basis and the only real question is God or atheism. This posture, establish during the Cold War, didn't anticipate the threat of Islam. However, not all conceptions of God are equally appealing. How, then, does a Christian argue that one should avoid Islam and take the path of Jesus? If one’s argument is purely based on faith you are at the mercy of chance as to whether you accept Christianity, Islam, or reject religion altogether. That’s a disturbing notion is it not?
Founding Fathers didn’t argue about religion given the vast numbers of religious beliefs from deists to Quakers. They argued about ethics and politics but they generally did so by using empirically-based reasoning. Even if they weren’t deists, they assumed if you understand the laws of nature by examining nature, you understand the laws of "nature’s creator." Settling differences by reference to reality and right reason avoids direct questions about theology. There was no doubt in their minds that if one discovered an ethical principle, just as if one discovered a law of chemistry, that one was learning about the laws created by "nature's creator." However, it was reality that settled the dispute, not textual analysis. The latter is pursued privately with one’s fellow religionists.
Essentially, the Founders embodied a tradition of ethical naturalism. It’s a tradition worth maintaining.