To those of us who disagree with "western theology" yet live by the rules of governments and institutions constructed around it; it is truly unfortunate that often we must argue within the box in order to try to free ourselves from it.
Christianity--in all of what it is, is assumed to be and claims to be--are a mere interpretations of the various bibles. When you receive the sermon while attending mass, you are receiving the word and then a mans (the priests) interpretation of that reading and often why he thinks it is relevant to modern life, this, that and the other.
When someone who has been judged by standards that they do not agree with decides that they wish to argue a point with a person of faith, often, in order for the conversation to go anywhere at all, the person in question must argue within the box. Sometimes they just wish to poke fun at these judgements and show how ridiculous they are, other times they really wish to say something, either way they just wish to make their point and be listened to in equal time with those who hold the opposing view.
The alternative to this is saying things to the effect of:

God doesn't exist.
Prove it.
Shut up.
Fuck you.

Needless to say, these attitudes are not conducive to intelligent conversation. Religions generally only welcome argument on their own terms (if at all), so don't be so shocked when you see it done well or in a way that is difficult to rebut.

If you are an atheist that prefers to argue with the measures underlined above, perhaps this has shed some light on the subject for you. If you are a scorned Christian, next time you are in church and the Priest gives his sermon; in the ensuing silence I would like you to stand up and shout to the front of the Church:

Hey Padre! I'm so glad you were able to talk to Jesus and find out how he feels about this issue!