Most religions by their very nature are about social engineering and control of people. So naturally the more fundamentalist that they are they more they are the supressors or repressers of sexual expression, and well as "art."

So religion usually ends up in the arguments about art/porn/erotica because they are usually the crusaders against it. However many societies in the past revered the sex act and it's many variations partly because sexual expression led to more population, which was a good thing. Besides, it was fun.

Even today fundamentalist religious types love to spout things like Sodom and Gomorrah stories and myths like the reason Rome fell was because of sexual decadence. So, deeply ingrained in any Judeo/Christian society or its descendents is the notion that sex is bad, demeaning, and evil.

Keeping religion out of the debate is pretty difficult.