I can't remember who I had this conversation with, but I do remember going over this ground before, so apologies if I'm repeating myself, but:

First, obviously Fraser is not going to have sex with anyone he isn't in love with.

Also, I can imagine Fraser having some sexual attitudes similar to those that a lot of us had in early adolescence -- where embraces and chaste kisses seem respectful, romantic, and loving, while anything remotely dirty seems disrespectful and unkind.

I can imagine someone (it's still Ray K. in my head) having a really good time tempting Fraser into getting dirty.