@rumborak: To me, the wording you chose is a bit odd and unclear. But if what you are asking is, am I predisposed to argue these types of things from a Christian perspective, and are my argumenst consequently biased to be consistent with my Christian beliefs, then yes, of course I am.
But let's take this post as an example. I was merely responding to the mistaken assertion that the Mithras cult likely influenced Christianity. I believe that is highly unlikely, and a simple timeline illustrates why. Again, various books foretell Christianity with varying degrees of specificity. The books of Moses were most likely written sometime between 1445 and 1405 B.C. And they record a monotheistic belief system and systems of worship that had been practiced and passed down from one generation to the next for thousands of years. Other books containing relevant prophesies are written from about 1,000 to 400 B.C. For the sake of argument, even denying that these books are truly prophetic, the timeline and the fact these books were very well-known by Christian writers and early Christians strongly suggests that these were the sources of the Christian belief system.
The Mithras cult, in contrast, is not known to have been firmly established until the first century A.D. Even if it existed for centuries prior (which, if I am not mistaken, archaeology does not support), it was not widespread in the Roman empire, including Judea, until the first century A.D., making it a very unlikely source for influencing Christianity, which was already spreading and developing all on its own during this time period.
@GP: Yes, in a sense, it is an "extreme rebuttal" for the reasons you mentioned. But at the same time, it was an entirely serious one.