I think the only my only concern with porn is that it turns sex into a sport or theatrical event rather that intimacy. While sex is a sport for some, in hopes of deriving self pleasure, I'm not sure self pleasure advances the cause of sharing and loving others.
It may be old fashion but isn't polyamory about connecting and sharing with others over self gradification?
Certainly always seeking self-pleasure to the exclusion of your partners needs and desires is not an indication of a loving, sharing, and intimate relationship, but sex is a multifaceted experience that is not kept in a static emotional or physical space. As our moods change, so do our desires. Sometimes what we crave is the sense of unity gained from slow, attentive lovemaking (grokking them in their fullness), sometimes it is a quickie, or maybe laughing playful sex, or the edginess of rough-play or one of any number of other manifestations of sex- and sometimes you just want a debauched bump-and-grind athletic fuckfest. Sometimes there is mutuality involved, sometimes one partner is the focus more than the other. But physically one-sided play that does not mean there has to be a lack of emotional intimacy. Ask anyone who gives intimate massages...
Consequently, I think its a bit unfair to try and pigeon-hole sex-as-sport as being inherently detrimental to intimate relationships. Even in one night stands, when the animal passions are possibly at their fullest flow and its all about the physical, I have had some profoundly connecting and emotionally intimate experiences.
I guess in my long-winded and rambling way I am just trying to say that you need to be careful about confusing the outer appearances (physical grunt-and-sweat sex) for the inner landscape (intimate connection). The two are related in strange and mysterious ways that are not always straight forward.
Regarding porn itself, I don't think porn is a completely innocent vice, but I think the democratisation of porn and its wide-spread availability has made it a lot more transparent and ethical and I am morally happy watching it. I have no doubt the number of porn stars that were exploited during the early days of the VCR revolution of the 1980s were a lot higher than they are now, even though there is a hell of a lot more professional porn being made today. Women are more educated and confident in themselves than they were 'back in the day', and there is a lot more scope to give voice regarding complaints and abuses through blogging and fan forums then there ever has been. Amateur porn is a bit more two edged. On the one hand, what could be more ethical and open than consenting adults freely distributing their sexual encounters? But on the other hand there is the blight of revenge porn, the purveyors of which are scum.
Also, at one stage I got quite friendly with a student health medical doctor and one of the conversations that came up was injuries caused by inexperienced attempts at anal sex. Svelt young porn starlets easily taking large members without any discernible preparation had given guys and girls an unreasonable impression of what is entailed (pardon the pun) with anal sex.
And speaking of porn, didja know the world's oldest surviving full-intercourse porn film dates from 1915 and is available on the web?
/Adam