Thomas Jefferson said it, yes. But in a COMPLETELY different context, Jefferson was basically saying different people have different God's and that's okay, they can live in America, the country isn't JUST for Christians, but it was founded by Christians who held Christian values and understood that Christian values were the most subjectively fair values to base laws off of.
Yes, I am saying everything related to the KKK was bad, their entire mission was the oppression of others in any way they saw fit. And yes, it's bad to say someone can't get drunk just because you don't like it, because unlike abortion, the only one getting drunk -barring any unforeseen circumstances or things like drunk driving- no one else gets hurt from a guy being drunk off his ass.
And no, the KKK was not a Christian group, they were radical White supremacist Democrats that PRETENDED to be to gain supporters, but once they got going they showed their true colors by burning crosses, lynching gays, blacks, and Catholics, and even burning down churches.
I'm not sure about joining the KKK now, but when interviewed, former initiates said "They asked us if we we're religious, we said yeah, they asked us what was our religion, we said Christian, they said no problem, we've fixed people like you before."