I had a discussion with someone on this topic not that long ago and some of the thoughts are still in my mind. My opinions mostly overlap with the ones already expressed in that it's a matter of personal preference. For myself I have never been comfortable with the practice of ERP. I just can't properly, I guess, dig that far into my soul for character content without the usual real life stuff that makes the situation. I can fake a lot of RP without the actual persons and settings existing but intimate matters are different.I could write smut but I couldn't properly navigate my fictional character through the act. At least, not in real time.
There are those that can, though, and use that ability to explore a facet of their character every bit as important as anger, sadness, greed, or what have you.
I only skimmed a little bit in the thread (sue me) but (and I hope I'm not just parroting someone that made one of the posts I didn't read) I think the contention on the issue is really only the result of peoples' reaction to people who abuse it. People who use RP as a chance to engage in some fantasy, possibly against the will of the other participant (as has happened to me on one occasion), which only serves them as a (to be crass) masturbatory aid. Which, of course, is fine between or among consenting participants. But there have been some people (there will always be such people) who abuse this aspect of the human genre just to get off.
Anyway, I think the rule should be the Bill and Ted "be excellent to each other" requirement and try to use best judgement when engaging in this kind of RP.
Just like how I don't make anyone watch as I lewdly count every new ISK credit as it comes in while I tickle my nipples.