Just yesterday while waiting to cash my cheque, I picked up a Jehova's Witness pamphlet and started leafing through it. Came across an article that said the Witnesses don't use the cross because they believe Jesus was crucified on an upright stake. (I apologize if I'm mistaken there, I think it was a jehovas witness pamphlet, not 100% sure)
In that context, if you are against the cross, then I can see why you would be against pentagrams. Also it's only natural to fear that which you don't understand.
So to help you understand, did you know that all religious symbols are based on the Platonic Solids?
The Jewish Star of Davis is in fact a star tetrahedron. Christianity's symbol of the cross is in fact a representation of a cube.
Christianity sprang from Judaism. Connecting all the points of the star of david makes a hexagon, and the cube (cross) can be viewed as a hexagon as well, which can be viewed as paying homage to it's origins.
Getting back to the pentagram, this is a representation of the symbol of Islam, which fits perfectly overtop the dodecahedron (the star fits over one of the faces while the cresent moon implies the rest of the structure). The 5 sided surfaces of the dodecahedron are the original inspiration for the pentagram, it has nothign to do with anything satanic.
All religious symbols are based on these platonic solids, but over time this has been forgotten. Like the telephone game, things get distorted more and more as they get passed on from person to person.
I don't really know where I'm going with any of this, and I really don't expect it to change your mind about anything. All I'm saying is your son's facination with this shape is perfectly natural. All physical matter, every atom and molecule is based on the platonic solids. There is nothing evil about them, it's just the way things are.
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