You keep saying "promoting porn", but I don't think you know what you're saying and why it's silly. Pornography is one of a very small handful of products that sells itself. There has always been a desire for porn, there will always be a market for porn. The internet showed this more than anything. We have this great system that people can use to exchange knowledge, and what is one of the top uses? To view and exchange porn. People seek porn out naturally, without influence from others. At the very least interest emerges through healthy sexual exploration.

Now to the "scientific effects". Have you ever heard the saying "everything in moderation"? Porn is not harmful if consumed in moderation. Most people do not ever become "porn addicts", even frequent viewers. Second, porn can have positive functions that overcome negative issues. For one example, it is widely supported that increased usage of porn leads to decreases of sexual assault and rape in communities. Also, porn allows people who are not in relationships to have some sort of sexual experience and potentially attain some sort of (largely harmless) sexual satisfaction. This is good thing, especially in the Western world where everyone is not guaranteed a mate, and indeed where less people, specifically men, are having sex than even in the 40s and 50s.

Also, do we or should we regulate or shun everything that has harmful effect, especially those things where the net harm is benign? I don't think so. One of the principles that conservatives are in favor of is freedom to choose, within certain boundaries. In this case, adults should be able to choose to view pornography if they wish and they should not be denied that right because the benefits to society outweigh the negatives, and any negative side effects are relatively benign.