Christians love to remake Jesus in their own image. It is our favorite pastime. Thus conservatives believe Jesus is a good ol' boy, blessing the nation state, preaching charity (not socialism!), and threatening hellfire and damnation for all those who have sex standing up because, as the old saw goes, it might lead to dancing! Liberals meanwhile imagine a tofu-eating, guitar-playing, peace-loving hippie with a poet's soul and a soft heart for prostitutes.
Both are obvious caricatures. Anyone who tells you they know exactly who Jesus is, and then proceeds to describe a guy just like themselves but with a beard and more gravitas, is a nincompoop. That's right I called you a nincompoop! What are you gonna do about it?
Our mental images of Jesus are idols, every single one of them. No one has a perfectly accurate understanding of this man who is by definition always beyond our comprehension. Still, is there nothing we can say about this image war between liberal and conservative Christians? Is it a hopeless stalemate?
No, I think there is a definitive fact, an aspect of the gospel story, which resolves the dilemma in favor of the liberal side: Jesus was crucified. He wasn't killed by a populist assassin for siding with the establishment. He was tried and convicted by the state at the urging of the religious elite, and he was executed as a rebel. No matter how you spin the story, no matter what you believe the content of his message was - it has to make conservatives uncomfortable that he was killed by the conservatives of his day.
Given that one fact, when invoking Jesus in present day disputes, we should never take seriously the idea that Jesus would side with the establishment. I don't imagine for a second that Jesus is in facile agreement with everything liberal Americans believe - especially where liberals are embedded in the status quo. But, if liberalism remembers its populist-reformist roots, it is far more likely that Jesus is to be found standing in a picket line, than sitting in a board room.
That should make conservatives very uncomfortable indeed, because conservatism is about reaching into the past to resist change in the present, for the sake of protecting one's own stake in the status quo. It is an ideology which cannot cope with the world-overturning kingdom theology of a crucified and risen Jesus Christ.
So, in addition to the track record of liberalism actually improving our society morally, there is another reason to be proud of being a liberal: Jesus is one.