The breakdown of Christianity for me, starts with the Bible. I think people spend a lot of time trying to prove teleological, cosmological, and other 'illogical' arguments in the case for "Christ." But those arguments do not point directly toward Christianity being true.
The reason we even talk about "God" in the Christian sense at all, is because of the Bible.
Without the Bible, you wouldn't know the name Jesus. You wouldn't know the Ten Commandments. You wouldn't go to church. And some think you wouldn't have morals! So why do you trust it as such a strong reference point?
The Bible was 'canonized' around 325 C.E. (about 275+ years after Jesus' death) with Constantine in charge. It was not "written by God." It was written by 40 different men that said they were inspired by "God" over a period of 1600 years, in 3 different languages! Also, no person that wrote the books of the Bible ever actually walked with, or met Jesus (except in visions or hallucinations). It was all passed down through word-of-mouth hope and faith.
At the time Constantine was overseeing the canonization or 'building' of the Bible, if he didn't agree with the text, it was thrown out. There are tons of 'scriptures' that did not make it in. A quick research on the Council of Nicaea will prove this.
So why do you believe the Bible? Why do you trust that what those men wrote down was actually inspired by "God?" I need more answers than just "faith" or "because they said they were," because so did David Koresh, Charles Manson, and Jim Jones, and Mohammad from Islam who wrote the Qu'ran, and you don't believe any of them.
So why do you believe the Bible? Why do you think it is actually the holy word of the Christian god? Why do you disbelieve the Qu'ran, and the Holy Vedas? They claim to have the same level of metaphysical inspiration.