They also deny that conservatism reflects Christian values and maintain that liberalism is truer to the teachings of Jesus Christ, especially in its alleged heart for the poor -- a point about which liberals, in my opinion, are most misguided, confusing the role of the individual with that of the government.
While I don't doubt that many liberals sincerely believe liberalism is "more Christian" than conservatism, they can't explain away the left's abiding discomfort with Christianity. That's because liberalism -- no matter how you sugar coat it -- is fundamentally incompatible with the Christian worldview.
Without preparing a flow sheet to compare the respective compatibility of liberal and conservative beliefs and policies -- such as abortion -- with Christianity, I refer instead to first principles.
I believe the main animating difference between conservatism and liberalism is that the former believes in the Biblically revealed sinful condition of mankind. Our Constitution's framers established a system of government around their belief that man-operated government had to be limited and held in check in order for freedom to flourish. Liberalism generally embraces a secular humanist (or enlightenment) faith in the general goodness, perhaps even perfectibility of man.
Conservatives accept that government exists as a necessary evil, to prevent anarchy, establish order and maximize but not absolutize freedom. Human beings within this context will be freer to minimize, but never completely solve society's problems.
By contrast, liberals place their secular faith in government to wholly eradicate societal problems (John Edwards will eliminate poverty in 30 years, following LBJ's 40-year, multi-trillion dollar failure to do just that).
The writings of the father of modern conservative thought, Russell Kirk, affirm these essential differences between liberals and conservatives. In his work, Kirk sets forth certain conservative "articles of belief." At the core of these, is an adherence to a Biblical worldview.
Conservatives believe in "an enduring moral order" and that "revelation, reason, and an assurance beyond the senses tell us that the Author of our being exists, and that He is omniscient; and man and the state are creations of God's beneficence. This Christian orthodoxy is the kernel of [Edmond] Burke's philosophy."
Also, "conservatives are chastened by their principle of imperfectability. Human nature suffers irremediably from certain grave faults, the conservatives know. Man being imperfect, no perfect social order ever can be created. … The ideologues who promise the perfection of man and society have converted a great part of the Twentieth Century into a terrestrial hell."
If you won't take my word for it, listen to Kirk: The differences between conservatism and liberalism flow from their competing worldviews.