Einherjar - Christians are not the only people with concerns about content or that question the point of such content. Concernes were also not exclusive to metal/rock, there was/is large concern with Rap attitude for many reasons, even amounst the black community. Metal concern did not solely focus on satanism either, there were others.
Having been a parent that raised a child, I will tell you many things suddenly come into play when we consider what influences we want around our children, this is a natural ancient instinct and I sure as hell wasnt going to fight it.
Myself I just question the point of such lyrics or antics. I dont apply to them and am quite comfortable with that. You said jepordize artistic integrity... I would say... "what integrity?"
You're right, it's not just Christianity. Plenty of different interest groups influence censorship as well. Feminists were offended by Nirvana's "Rape Me," which was actually why it was censored. However, the song is actually an anti-rape song written by Kobain. He never meant it to be offensive.
This leads me to my next point. "What integrity?" It's possible for bands to be very poignant in their lyrics and yet also cause offense. Questionable lyrics have a very important purpose. Usually they're the most important lyrics. Admittedly, there are artists whose lyrics offer nothing in the way of intellectual thinking (rap music and metal such as goregrind, as you've said); but there is plenty of metal with intellectual, meaningful lyrics that would never be allowed on major American radio stations. Observe Kiuas, a Finnish metal band. They never swear or sing about sexual material. Some of their lyrics are violent, but not in a gratuitous way at all. However, this is the chorus to one of their songs:
"Fire rains down from the heavens,
Pouring down on those too weak to learn.
All the ruins of the dead religions
Standing tall as the enslaving doctrines burn."
These lyrics would never be played on major radios in America, because the Christian church would not allow it. However, the lyrics are far from gratutious or pointless, and changing them would alter the intensity of the song. Kiuas are a vehement, iron-willed act, and changing these lyrics would compromise their integrity. Personally, I don't think they would submit to ever changing the lyrics; but that just means that they'll suffer less radio play and marketing opportunities. Therefore, they won't sell as much. This is what I mean by the integrity of the artist. Their art shouldn't suffer.
As to your point of being a parent: I agree that there are certain things you don't want your children to see or hear; but that's your job. Take the time to listen to an album before you buy it for your kid. You can return it if you decide it's inappropriate. Read up about a movie before you let your child see it. They have excellent reviews in the paper. Personally, I believe that film ratings should be done away with. So many great films are edited because the MPAA initially gives them an NC-17 rating. They have to cut the film down just to get an R. Many film companies won't let a film go with an NC-17 rating because it severely hurts marketing and advertising. Television stations and certain theaters won't pick up a movie that's rated NC-17. The director can keep his/her film intact, but it will hurt sales. Or they can cut material from it, but it ruins the integrity of the film.
Critics should still view films; every film that's in the theaters, as soon as they come out. This wouldn't be hard, only a few new movies come out each week. There should be no rating attached to the film, but the critic should offer a detailed account of what objectionable material is contained in the film. Based on this report, parents should judge if they will allow their kids to see a film (or if they even want to).