I have a problem believing in things I can't see. But I'm not alone.
When something hits me in the head- and I didn't see it?- I respect it. Ask anyone over 6 feet tall (come to think of it, my foot is at least a foot long- now that you mention feet) how many times they've been smacked in the head. Ever have a car drive over your foot? Hurts like hell. If a way exists to utilize another 'sense' it should be discovered. Otherwise, we'll look like dummies to those 'in-the-know'.
Different believers have different spiritual gifts, but to believers who have been exposed to spiritual warfare and directly exposed to demons, that is an undisciplined worldly reaction to unbelievers.
What most unbelievers fail to understand, is that the love and patience believers exhibit when communicating the issue to an unbeliever, is frequently misunderstood and associated with naivete and foolishness.