To begin with, pornography is extremely addictive. It could be due to the fact that we humans desire for sex as it is a natural course in our life. In pornography, models with pretty looks and perfect curvature are enlisted to feature in the videos, as a way to attract more users to view them. This makes the users predominantly teens are still not mature enough to control their inner lust towards sex to indulge themselves pornography as long as there is no intervention from a third party. It could take the users hours to browse through the materials or videos that they think are most suitable for them. The users tend to stay up late and end up waking up feeling groggy and tired the next day. Plus, the release of sexual desire via masturbation further drags the users down, making them feeling mentally and physically exhausted to perform their works well
Watching excessive porn (few times a week - once/few times a day) is bad because it literally rewires your brain and how you react to sexuality. It not only objectifies both men and women, but puts an unrealistic standard on sex. While it should be recognized that porn "isn't the real thing" and you should be able to separate real sex from porn sex, people that watch it in excessive amounts have a harder time doing just that. Porn causes a person to focus on their own sexual needs and their own preferences, which isn't a bad thing unless you're ignoring your partner in the process. You focus on how the sex looks and the positions you're doing instead of how it feels for you and the other person, or you forget how to pleasure your partner because you're so used to only pleasing yourself. You become desensitized to intimacy and confuse the idea of how intimacy between two people work. It can become an addiction, just like almost anything else, and I do not believe it to be harmful in small doses, but it can become a serious problem.
How exactly would pornography be harmful physically? Especially in light of modern medical evidence that occasional masturbation has a positive affect on general mood and health for both men and women. It has also been demonstrated to have a soothing mental affect, helping to alleviate day-to-day stress and anxiety. Unless someone is into kiddie-porn or they simply sit around all day and do nothing else with their life than view pornographic material I don't see how it possibly could be harmful to anyone.
Like anything in life, whether it be smoking, alcohol, gambling, gaming, even working, too much of anything will have negative affects on your health and relationships, if it is done to excess.
With pornography, i would say it's like watching any movie, as long as you accept before you watch it that it's not indicative of real life behavior, then it can't really harm you, before the days of the Internet, people would still visit strip clubs and look at magazines, even in the days of ancient Egypt, they have found pornographic art, i think it is in the human nature to be intrigued and curious about their sexuality.
It's when the addictiveness and excessiveness comes into play, that anything becomes harmful, there is nothing wrong with having a drink of alcohol, but you can get addicted, there is nothing wrong with having a gamble, but you can get addicted, Pornography is no different.
There are no physical issues related to masturbation or viewing pornography, unless if you did it like 10 times a day, and even then the pain would be temporary, i think the worst thing which can happen, is that it gives people an unrealistic view of sex, but you have to give people some credit to realise what they are watching isn't real, just like they don't go out and murder pedestrians after playing GTA, a good movie to watch on this subject is Don Jon which highlights the dangers of excessive and addictive pornography use.
So overall i would say no.