If you Christians can't even agree amongst yourselves, why should anyone else believe you?
- It's a fair question--according to one estimate, there are some 41,000 Christian denominations, representing about 20 major branches, each of which is a different interpretation of Christianity.
- However, most of the differences among Christians are not questions having to do with the ultimate truth of central doctrines. It's not as if we don't agree on the existence of God, the nature of Christ, the value of salvation, or things of that nature. (As opposed to Christianity's differences with other world religions which are disagreements about such ultimate questions. This means that not all world religions can be true. If Christianity is true, then Islam and Buddhism are not, in a way that does not hold when various Christian denominations are compared.) Christianity's many denominations all hold to a common core of doctrine rooted in the apostolic teaching in the New Testament; differences tend to be about rather more minor, peripheral points of doctrine, for which the New Testament texts could plausibly be interpreted in various ways.
- Further, despite our surface differences, all true Christians are actually united together in the highest possible sense. If one is truly a Christian, then that person is mystically united with Christ and is one with all other true Christians, of whatever denomination they may partake.
If Christians are riddled with moral failures--as you obviously are--why should anyone believe you?
- It's true that some Christians have done some truly awful things. The question, however, is whether those awful things are actually attributable to their being Christian. In most if not all cases, it's not a correct understanding of Christian doctrine that underlies their heinous acts. Their behavior is not explained by their faith, but rather by their humanity. Christianity actually predicts that all people--including Christians--will deal with the ongoing effects of their own sinfulness. That's not to dismiss such behavior or say it's okay, but simply to point out that this doesn't add up to a valid argument against Christianity.
- This question also tends to fall into the ad hominem fallacy--pointing at one person's moral failings to discredit a set of truth-claims, rather than assessing the truth-claims on their own merit. Don't base your life on a fallacy. Yes, Christians will struggle with sin. But it doesn't follow that God isn't God and that Christ isn't Lord.