This is a criticism many non-Christians have about Christianity, and that many Christians have about other Christians. It also gives anti-Christians much to make fun of, and makes it hard to discuss the truth or error of a Christian's message, since it is hard to find two Christians with identical messages. There are different solutions to the problem. Some people say, well, if the adherents can't agree about what they adhere to, it must all be hogwash. Others say that the core truths are constant, but the specifics vary from person to person, as though some truth was relative. Some people say that it is all true, and ignore the contradictions. Some assume they are right, and refuse to consider any other possibility. My solution is to choose truth carefully, and follow what I believe to be the promptings of the spirit, and differentiate between what I hold true, and what I hold likely, trying not to confuse the two, and not hold anyone else responsible to live according to what I accept as true, even if I believe they are up in the night.