It's just anti-establishment, anti-religion imagery. It's an identity. Why gangs have colors/patches etc. There was a reason that the Nazi's had Hugo Boss make SS uniforms, and they were visually unique and powerful. It garners attention from the rest of society.
The upside down cross, baphomet, pentragram, it's nothing more than people looking for answers, expressing their anti-Christianity stance, and it gives forth an intimidating image.
Behind the image is just regular people trying to find their way in life, like everyone else. Maybe they're just a little more lost.
