I've certainly seen conversations in the chatterbox where the large majority of participants were not religious, to the point that I was a bit surprised, perhaps due to having gone to college in Utah (: I doubt you'll find many of those participants proclaiming their position regarding religion on their home nodes (and I'm glad of that, FYI). So I think your view of a prevalence of Christian declarations to be, at least in part, due to how likely holders of certain beliefs are to consider their proclamation of such as being acceptable (to themselves and to others perceived as likely to visit PerlMonks).
I'm glad when the topic of religion does not come up. I certainly refrain from stating my positions on religion here. Although I've been known to play "devil's advocate" to people including on religious points.
I try to be respectful of others' religious beliefs if for no other reason than that anything else can easily be quite rude. Most of the time, this just means keeping my mouth shut (or "fingers mute", if you want to be more literal), which suits me as I don't care to hear the vast majority of conversations regarding religion whether an argument, agreement on any position in the huge field of possible opinions, or something between. Frankly, these are usually quite unoriginal and are often uncomfortable for many. As such, I prefer they be more often restricted to areas where participants are expecting such (that is, somewhere other than PerlMonks).
I'm certainly not hoping for people to remove any mention of religion from their home nodes nor trying to prohibit the topic of religion from the Monastery (juxtaposition of terms intentional). I'm just expressing my personal preference for a scarcity of religious discussion, and I can certainly avoid the chatterbox or threads when required :)