Theological exclusivity and their persecution complex. It is rather fascinating that adherents to the largest belief system on the planet would feel persecuted, but when combined with their claim of being the "one true faith", a Christian's persecution paranoia makes any attempt at meaningful spiritual dialogue null and void. Their capacity to dish out criticism of the "flaws" of other faiths is directly proportional to their inability to accept criticism of their own, and they seem incapable of defending their own faith by any argument other then "The Bible is inerrant, therefore it is True and all other religions are false". And yet they invite such criticism by vocalizing their religion at every possible opportunity, thus making conflict unavoidable.
Basically any attempt I have ever had at discussing religion with a Christian comes down to this"
Christian: "The Bible is the one true faith. Jews, Muslims, Hindus, Buddhists, Pagans, Agnostics and Atheists are all going to hell because they do not accept Jesus Christ"
Me: "But wait a minute, what makes your religion anymore legitimate then those other faiths? If you take biblical inerrantcy out of the picture, since the Bible cannot be used to validate itself, there is no objective evidence that validates Christianity above all other faiths"
Christian : "I..... I don't know..... Stop persecuting me for my beliefs!"
Me: "You are the one who brought up religion, and how yours is 'right' and mine is 'wrong', in the first place"
Christian : Well.....I was just.....ummm...(trails off incoherently)
I would just like to add that 1) I never bring up religion in the first place in these conversations, and 2) I do have many friends and family members who are Christan and we get along just fine; we just try to leave our religion out of the picture when we are together.