While I agree with them in this case, why do we care what the founders thought? Originalism is not a real philosophy, just a weak appeal to authority regarding a group of people that did not and cannot represent the people of the modern world.
It's the "conservatives" that keep making those appeals to authority. Founding fathers this and founding fathers that, because they have no real arguments. Showing that even those arguments are fallacious is justified.
Most of the people I know make the argument that this has ALWAYS been a Christian nation which I'm quick to point out that it was designed to be separated because of their own experiences being persecuted for their religious beliefs.
Having these quotes with some legitimate sources would be fantastic argument material for me though. Hoping someone digs these up as I can't at the moment.