Christians don't support infanticide, gay marriage, taking authority from parents and giving it to govt., etc. Democcrats do. They are therefore opposed to Christ. They don't recognize His authority, but recognize and exault govt. authority.
Christians accept Christ as their Lord and personal Savior. That does not mean that they we are free of sin. Coveting is a sin at least equal to the ones you mentioned above I, despite my best effort – from time to time – have been guilty of that sin; I am still a Christian. While denying a sin is a sin is hypocritical, it is – technically – not a greater sin than your average sin.