It is true that Christ's teachings were entirely contrary to the old testament. And it is true that the teachings of the old and new are completely irreconcilable. But Christians still have them all together in one, schizophrenic, incoherent book which, if enacted into actual law, would result in a disastrous and despicable theocratic state.
Thank God for the separation of church and state. Yes, from all churches. It makes Liberal Democracy possible.