Quote mining aside, there are many of these same Presidents that expressed Christian ideals as well. Some of these are quote mined very much out of context, so are dishonest.
You can Google any one of these men's religious views rather easily.
For instance: George Washington was not only a member of his church, he was also a councilman and asked soldiers to fast and pray to God on a day Congress laid out for it. See here His stately letter to Indians regarding their instruction: "You do well to wish to learn our arts and ways of life, and above all, the religion of Jesus Christ. These will make you a greater and happier people than you are. Congress will do every thing they can to assist you in this wise intention; and to tie the knot of friendship and union so fast, that nothing shall ever be able to loose it."
John Adams' quotes including the treaty of Tripoli were written to appease Muslims who were attacking American ships and history recognizes it as a weakness, a caving-in, to pirates. To redress this as a quote-mine, is inept at best, and dubious by moderation, in attempts by atheists.
I can go on and on, but quote mining the Presidents by atheists has always been an exercise in lying, most often of purpose, which makes it truly evil. It is sad that anyone would feel the need for this kind of unethical platform. I suppose it is politics, but we try not to vote for the ones that are so obvious about it. I'm not sure if you are doing this on purpose or ignorance, I just lift it up in the proper light it deserves.