Yeah didn't have a big problem with it, though I admit that some people on earth absolutely would, but then those aren't the people that would sign up for such duty.
And the show does go and show two Earth characters having difficulty (one greatly) with the idea that this "random soldier" is the person they claim. SO the show does actually cover its basis, in this regard.
I mean to this day you see people with a wide range of what they find acceptable sexually, so I don't see a problem. Hell I know some one who performs a sexual role for a couple, after one of the partners was no longer able to perform a sexual role in their lives after a serious car accident. It seems to work for them.
And think even Trek has dealt with this with the beings that assumed (with initial approval from host, though probably not for those sorts of activities) control over the host bodies of Kirk, SPock and female crew member back in the 60's.