I don't have adolescent children yet, so it hasn't come up, but I'd rather they didn't, and will tell them why. I would think with adult children it would be out of your hands what they do. Presumably even if they're still living at home they would have some privacy being adults.
My concern isn't so much whether it's bad for men as that it's bad for the people (especially the women) involved with making it. People talk about personal choice, but, without wanting to get into it too much here, some women are definitely hurt by it. A number of porn stars have spoken out about their experiences. http://fightthenewdrug.org/10-porn-stars-speak-openly-about-their-most-popular-scenes/
I've also read that watching porn while young can give teenagers a warped idea of what sex is and should be like, which is pretty much bad for everyone. There was an Aussie documentary I can't remember the name of at the moment where they interviewed a number of teenagers and found the boys were confused that the girls didn't like the things they had seen porn stars apparently enjoying and girls were upset that young men thought it was okay to try things like anal without consent. Melinda Tankhard Reist's book Big Porn Inc is a good one on this topic.
Great minds think alike - I think fightthenewdrug is a fabulous website. I don't know if you're familiar with Dr Gail Dines' work, but she's certainly a leader in the field worth looking at.
There is not a doubt in my mind that watching porn warps teens' views of sex. Even as an adult, I've had porn threaten my views. And, if we know that the standards promoted by the beauty industry affect girls as young as four, it would only make sense to admit that porn similarly affects teens' ideas, expectations and perceptions.