Conservatives are in denial, as your first answer illustrates beautifully.
Plus, particularly if they're also religious, they scramble for the moral high ground and come on so self-righteous it's like they're surrounding themselves with a cloud of holy incense through which it's impossible to discern anything but vague shapes. So you don't get subtle arguments from conservatives. Abortion is baby murder. Gay marriage is perversion and it will be the death of America. The Bible is the word of Gawd.
LIberals prefer the clear light of day, where things are complicated, where each moral case needs to be decided in the light of circumstances, and the appeal to absolute principle is replaced by subtlety, rational argument, and the recognition that life is often untidy. But you can't work with that mindset while holding a fundie view of the Bible, which is the real bugbear.
I offer this reply in a spirit of humility and tolerance, as a true liberal should....