***If your point was that people can really be judgemental and feel free to cast stones as if they were perfect and without sin, then yes, I got your point.***
No, my point is that if these bands mock the One who died for you with their evil persona, themes, costumes, art and lyrics how can you continue to count them among your friends?
Whether a particular such piece "mocks" or "exalts" is, granted, the $64,000 question, but the devil (or the Christ) is all in the details.
If by "mocking" you mean wearing black, wearing crosses, and singing about God being the only way to Love, then I guess I'm guilty as charged.