Peripatetic journalist of religion Terry Mattingly has a nice column that aptly summarizes the reasons why this word should be retired from contemporary usage. Blessedly he quotes the ultra-blessed Alvin Plantinga, whose analysis culminates in this definition:
Its cognitive content is given by the phrase "considerably to the right, theologically speaking, of me and my enlightened friends."
We'd quote more, but that would spoil the fun.
In the meantime, we simply ask gentle readers to engage in a bit of self-awareness that just about anyone can be someone else's fundie, that many such judgments are made more on the basis of fashion and taste and social class than substantive disagreement or critical thought, and that one disgraces oneself by relying on such lazy rhetorical tropes, disproving the very enlightenment one claims when one uses them.
Postscript: the insurgent, not-so-gentle reader who awhile back was littering our comments with the other f-word has not made a recent appearance. If that person decides to continue her self-defeating exercise of hostility against parental figures by so doing on this post, we say that we have already anticipated what the witticism ought to be: the present participle of the primal f-verb modifying the plural of the religiously condescending f-noun. To intensify, go for the common compound present participle that embeds a direct object. If you're going to use vulgarities, at least use them properly and fluently.