Porn sites here in Philippines are already banned a few months ago because of it's bad influence especially to the millenials. But getting porn sites to accept bitcoin is another story. It is not acceptable. It is not a wrong practice or use of bitcoin. We just use our common sense. Why we use bitcoin to purchase something that is not good for everyone.
You cant blame anyone on where they would like to spens their bitcoins since its their money after all and they do have the freedom on where they would use it either on good or bad. Porn isnt bad at all since every men do need it 
. As long it doesnt affect your mentality towards it then it should be fine. Porn sites are accepting bitcoin already nowadays but i dont think that this would really be worth of to spend it on porn industry since we can able to watch some porn for free maybe not in premium but it would be a big save up to your btc.