burning down a crack house...
is an act of vigilanteism against a clearly illegal operation (crack house). I believe in working within the system and I would frown on the vigilantes unless they were acting after the proper authorities failed to act. Then I might sympathize with them but they should be ready to pay for their own crime.
A porn house is not illegal (in this case anyway) and no one has a right to intervene on moral or religious grounds. We rid ourselves of things like porn houses by not patronizing them and doing what we can to convince others not to patronize. As long as there are people that want to pay for filth it will be available but there are no such stores in my neighborhood and if there were they wouldn't do much business.