I think you are right that there is a danger for the left to be biased in this way. Just like there is a strong bias on the right to selectively pick what was p

I think you are right that there is a danger for the left to be biased in this way. Just like there is a strong bias on the right to selectively pick what was part of the "good old times" up to the point where the whole idea becomes complete fiction. If we engage in a little bit of theological scholarship then it becomes clear why the trust in our own myths can sometimes be low. In the history of Christianity there has been so much political maneuvering and power play involved in the way these myths ought to be told or not told that most people question any truth those myths could hold purely on that fact alone. Then you also have devout Christians who would probably call Jesus if he was reborn today and said precisely what he said in the bible a socialist. So if the long history of the church and its religous wars didn't scare you off, the "Christian Love" of the loudest believers might just do the trick. With other cultures we don't know all that political bullshit and scheming which mind lurk behind their myth, so we have a different, less negative look at it.