I don't think that's supportable, especially when we are talking about humans. Procreation is most definitely not the only reason for sex. In the animal world we can look at the Bonobos, sometimes called "pigmy chimpanzees" (incorrectly so, as they are a distinct species but they look very very similar). Their social interactions center largely on sexual interaction, including between members of the same sex.
At any rate, I think the mistake is in believing that there are only two sexes and one sexuality. In my opinion, there are more than that. There are male and female and heterosexual, but also bi and gay as real sexualities that ought to be included in the list. Trying to make hetero and "the" sexuality is a mistake and as long as we keep trying to have only one catagory for that, well we are just gonna keep having trouble with it. I believe that bi and homo and possibly some other sexual orientations that don't fit quite so cleanly into these categories, are entirely normal sexualities. Just because they are found less commonly in society doesn't mean they are not normal.