So, according to the author of the July 16 letter, "Founders would detest abortion," the whole reason America was founded was to protect the unborn from abortion? Religion was but one of the reasons people came to the colonies in the early years. Their idea of religious freedom was much like fundamentalist Christianity's view of it today. Religious freedom for them. As a result, the colonies were segregated by religious affiliation, and yet religious tension sometimes developed between colonies anyway.
Religion played little into the founding of this country. The Declaration of Independence and the eventual war of independence started as a result of excess taxation and interference in colonial business. The Declaration of Independence is not a founding document. While it is an important document, it was in reality a letter to the king of England announcing the colonies' intent to sever relations with England and form their own government.
Terms like "Creator" at that time were seldom used in reference to the Christian God, though they were commonly in use by deists who did not believe in Him. Washington, Franklin, Jefferson, Adams, Madison and Monroe were all deists or unitarians and did not believe in the Christian God.
As to their opinion on abortion: Franklin, Jefferson and Benjamin Rush, a signer of the Declaration and medical doctor, all wrote about abortion but never against it. Rush described it as the equivalent of coughing up phlegm from your lungs. Seeing us today, they'd probably wonder why more abortions aren't being performed.