I've been having a lot of luck with this lately:
Christians In Name Only.
That's right, CHINOs.
It's easy to use. When someone mentions Falwell, say, "Oh yeah, he's a CHINO. Too bad he's not a real Christian."
More after the break -->
There have been a lot of terms used to label self-professed Christians who seem more interested in engaging in politics and, in general, un-Christian behavior than they seem to be interested in living a good Christian life.
This one is good and simple. It serves the dual function of identifying the Falwells, Robertsons and Dobsons as the hypocrites they are, while not alienating those people who do profess faith in Christ and live their lives accordingly.