if you're equating the devil with heresy, then it works both ways.
do you not accept the revelation of joseph smith or the prophet (pbuh) or the pope? how can you assert that your truth is the one truth? because of your inner voice?
anyways, when i looked closely at the source of "evil", let me tell you what i found:
- a bunch of people acting selfishly, because that's what people do (see milgram experiment, stanford prison experiment, the bystander effect and the trolley experiment)
- a bunch of people selling the occult because there's always a sucker (see cold reading and the forer effect, ouija and the ideomotor effect etc)
- a bunch of people killing one another in the name of their particular deity (see the death count of god vs devil in the bible)
seriously. who needs a devil when the deities of fundies have provided much more incentive to kill throughout the ages? in that sense, perhaps listening to "the devil" (not really sure what that is) isn't such a bad thing?