I'm a hardcore atheist, secularist, Jesus-wasn't-that-great rationalist, and I think the premise is ridiculous. I'll happily debate religion, but there are plenty of devout Christians who believe in liberty. A lot of the forerunners of classical liberal thought have their roots in religion- the King is below God's law, natural rights are a divine gift, the Protestant individualization of faith, etc.- and a belief in human liberty (while I don't find it in my reading of the Bible as a whole) can and has been justified on a scriptural basis- 1 Sam 8 is a great anti-state rant in the voice of the OT God himself. Judge Napolitano is a pre-Vatican II Catholic (his professed love of "Ann" Rand notwithstanding). Ron Paul is a conservative Christian. A lot of the founders had great Enlightenment skepticism of Christianity, but aside from Tom Paine and a few others they were not atheists, or even anti-Christians. The Bible has motivated a lot of horrors in human history, but it has also motivated many great defenders of humanity.
So, yeah, Christians can be libertarians, just like Jews and Muslims and Buddhists and Hindus and even us lonely atheists.