(Rant mode activated. Beware. Insincere apologies forthcoming.)
Happily, this does not apply to all fundamentalists, just most of them. There are no specific methods to identify in advance who these fundamentalists will be (that I currently can see), other than to engage in conversation first and the scenario just described will usually become obvious. You will probably not need any help in this area, unless you are one already.
2. Don’t always expect any interest on their part, or even the courtesy of a reply.
There are multiple reasons for this. Usually it boils down to the idea that said fundamentalists find themselves entrusted as the sole guardians of truth, which must be defended at all costs, remaining impervious to mere human reasoning and the inherent deception of a secular (to them) point of view. Please understand, the humility of the fundamentalists compels him or her to share the portion of truth entrusted to his or her own care, and when resisted, to patiently give one or two admonitions to repentance before whipping out the trustworthy all-purpose Stamp of Heresy TM. Also understand that such stamping need not occur publicly, but can be accomplished virtually in the fundamentalist’s mind without manifesting any physical evidence of its occurrence.
3. Don’t necessarily expect much engagement with ideas or even the Scriptural texts themselves, beyond the casual copy and paste prooftexting which has proven so popular and effective in terms of expressing majority opinion and reticence to any minority viewpoints. A text without a context is a prooftext, as someone has foolishly said, because prooftexts are self-evident, context is irrelevant, and why do we really need to discuss the text anyway? At these points, I typically try to interject the concept of the sacredness of tradition, without much success but no small amount of personal frustration.
REMEMBER: If you are NOT a Fundamentalist, then my good sir or madam, you are simply MISTAKEN.