|The point of this is (I assume) that your boyfriend is talking to his ex online and he's talking to her about sexual things and you don't like it and would like it to stop? If I'm correct then it doesn't matter what any of us think (BTW, I think its inappropriate and it crosses what most committed couples would consider a relationship boundary not to mention that it's totally disrespectful to his primary partner). What matters is that you don't like it (if you don't) and that you should tell him it stops or your relationship with him is just a farce that he is, like I said, disrespectful about and acting inappropriately for anyone who is suppose to be in a monogamous, committed relationship.
That being said: Just exactly what IS the point of your questions? What do YOU hope to gain by finding out what men that have nothing to do with you and your wants and needs have to say?
“The willingness to accept responsibility for one’s own life is the source from which self-respect springs.” ~Joan Didion