Many (though by no means all) liberals don't see liberalism as an ideology, but rather as plain old human decency and common sense. Daily Kos blogger Ed Martin took that viewpoint to an extreme this past Tuesday.
Martin doesn't think Republicans are qualified to call him and his ilk liberals. He wonders, "Why should any rational person allow themselves to be defined by people who have been wrong about everything?...[P]eople who proudly demonstrate their pathologies, sociopathy and psychopathy, every day."
Given that Martin finds conservatives sociopathic and psychopathic, it follows that he would consider liberalism synonymous with normality:
...If being defined as a liberal means the ability to recognize that there are other people in the world who are different from me...then being liberal actually means just being normal and ordinary...
Republicans, due to their pathologies, are unable to recognize as human anyone who differs from them in the slightest way. This is the essence of Republican inhumanity. It's called conservatism.
...As far as I am concerned, there are no liberals, there are just ordinary, normal people and then there are Republicans...
Martin alleges that GOPers are in some ways not of this earth:
The Republicans want to place themselves along with us on a scale that they define to try to gain some pretense of humanity by association...I think we need to recognize that Republicans are so far from any human attributes that they can't be placed on any scale that includes us ordinary, normal humans. They are not left, they are not right, they are not center. In fact, they are literally eccentric. They cannot be fitted onto any scale representative of the humanity of this world.