I think there's a subtle difference. While dogmatic is often used when in context of religions it's not exclusively related to religion.
Google's definitions of religion:
>the belief in and worship of a superhuman controlling power, especially a personal God or gods.
>a particular system of faith and worship
>a pursuit or interest to which someone ascribes supreme importance
and of dogmatic:
>inclined to lay down principles as incontrovertibly true
I think the most precise use of religion is in connection with faith or a core belief system and lifestyle (which some open source advocates certainly fit), while strong positions in a particular topic or narrow scope, e.g. the GPL, tend to be better described as dogmatic.
Which, reading back to the parent comment and the scope of the thread, I guess either could be used fairly appropriately.
A better place of where I think dogmatic would be the preferred wording would be in reference to tabs vs. spaces or vim vs emacs.
Of course, if you have a more favourable view of religion than me, you might disagree.