Christianity is not what is on the line here. It is human error. Anyone truly living a Christian (Christ-like) life will tell you the purpose in life is to reconcile people to their Creator, God. The belief is that Christ died and rose again for the purpose of bridging the gap between man and God.
There will always be people who prefer to leave a gap, and there will always be human error, in any endeavor. Without human error God couldn't show his grace and we couldn't learn to forgive.
Jim and Tammy Bakker, Oral Roberts and Jimmy Swaggart, as well as every other person on earth, have proven we are human. Despite how close we claim to be to God, or how far we are from believing God exists, we are human and we err. A quote not found in the Bible, but surely fitting for this situation goes, "To err is human, to forgive is divine."
As far as those poor souls who blindly send in money to TV preachers, they need to draw their attention to a local church or organization, so they can keep the preacher in check at all times, using the Bible as their guide if they're Christians.