And now that I have your attention, here's a bit of explanation: Far too many religious people out there practice in a way that strikes me as akin to the devil worship fundie Christians like to call out on anyone who disagrees with them. Or plays D&D. I'm not being really all-inclusive, merely quite broad, since there are weird 'modern' religions that turn their deities into some kind of metaphorical vapor, but they're a different topic for a different time.
[Viking] Anyway... [/Viking]
Here are some of the parallels I see between a lot of religions and devil worship:
1. The entities they align themselves with are evil: There's no getting around it. A lot of the deities out there are big into violence, discrimination, authoritarianism, and so forth. They have to perform all sorts of acrobatics to fool some of the kids. Big thing that got me out of church was a preacher who tried that about Hell at a time I thought everyone there had the moral decency to abolish Hell and other nasty parts from the Bible.
2. They make a pact with the entity for selfish benefit: Pretty much what Heaven is about. They get eternal happy juice injected into their ethereal veins after death because they allied themselves with the right entity. They typically aren't willing to share their alleged utopia with other people, since they tend to agree with the big man's arbitrary deadline of ~80 years (less for undeveloped countries), barring nasty circumstances that typically lower it.
3. They (allegedly) get malign powers they're willing to use against anyone who displeases them: There are plenty of people out there willing to pray for very not-nice things to happen to their enemies. If something bad does happen to one of their enemies, they'll typically give their deity credit and take some for themselves for rallying acolytes to pray for it. Happens especially often with big natural disasters.
4. Access to malign powers is typically performed with hand gestures, occult materials, and foci. Verbal components (including unison chanting), somatic components (clapping hands together, crossing selves, bowing in rough direction of a rock, that sort of thing), symbol, enchanted water/oil, idols, altars, etcetera.
5. False miracles/wonders/whatever: No shortage of fakery in the religion industry.