I think the title of this article is wrong, but the quotes are good ones.
It is entirely possible to be a Christian and agree with these quotes, to say things like this, and to live a life of acceptance of other people. To claim that this is proof that our founding fathers were not Christian is wrong.
It is also wrong to say they were all Christians. We can't ask them what they believed. We can gather certain ideas of their beliefs based on their writings, but unless one of them said "I'm not a Christian", how can we say they weren't? Also, unless one of them said "I am a Christian", we really can't say they were. All we know for sure is they did not want anyone's personal beliefs be the law of this land.