I looked over the articles. From what its saying, yes, theres some negative effect to watching porn. However, the mere fact that sexual crime decreases when accessabilty is better, is enough for me to support it. What you tell others is your business, but when it is shown that in developed nation sex crimes decrease as porn use increase, its a hard to say that it should be allowed, so im glad that isnt what you are saying.
As for cultural differences, tests were done in the US, Canada, Japan, Denmark and Australia. All very well developed countries, and tests showed the same results, as internet access increased, rape decreased.