A curious trait of traditional Indian and Persian beliefs is that they reflect diverging interpretations of that exact same things. For example, in Vedic beliefs, there are the devas, which are typically beneficial dieties, and there are the asuras, which aren't strictly evil, but are more likely to be a problem for you than a deva is. In Zoroastrianism, there are the evil daevas and the good ahuras. Yes, devas and daevas, asuras and ahuras. These words share the same Indo-Aryan linguistic roots but have come to mean the exact opposite of each other. Or, as a friend of mine said, "Looks like someone had a big falling out..."
This came to mind today as I read about the Yazidi. The Yazidi are a minority religious group largely of Kurdish ethnicity, with about half a million believers. The Yazidi faith shares many similarities with Islam (and, by extension, with Judaism and Christianity), but with at least one notable divergence. The Yazidi believe that God made the world, then made seven angels to take care of it, the foremost of these being Malak Ta'us. When God subsequently made the first man, Adam and ordered the angels to bow to him, Malak Ta'us refused, citing his own divine origins as grander than the dirt from which Adam was made. God rewarded him for this choice by putting Malak Ta'us over the other angels, the logic being that it was a test -- after all, if God had really wanted Malak Ta'us to bow, the angel would have had no choice but to bow.
So why does this matter? Well, in the Koran, God makes man, tells the angels to bow, and Iblis (that is, the devil) refuses for exactly the same reason and is cast out.
As a consequence of this particular different interpretation, the Yazidi have been widely called "devil worshippers." It probably doesn't help that their other name for Malak Ta'us is Shaytan, which is explicitly what the Koran calls the devil or devils.
There are many examples of one religion's members assuming another religion's dieties are false (usually) or bad spirits (sometimes), but I think it's fairly rare to find this kind of explicit flipping of a diety's role.