Interesting argument out forward here by Mark Dooley;
The fact is, of course, that heterosexual sexuality is essentially different from its homosexual counterpart. While both are potential expressions of love, and while both are sources of pleasure, only heterosexual union is intrinsically goal-directed. That is to say, only heterosexual union is capable of natural procreation. ”Put simply, marriage is not a culturally-formed institution but one which has its source in the requirements of nature. That is why it is simply mistaken to argue that ‘all forms of sexuality are completely equal’. For this is to imply that a form of sexuality which has no intrinsic aim is equal to that which does. Altering the definition of marriage so as to include homosexual union is not, therefore, merely a cosmetic change. It is to radically redefine the very meaning of the institution. And it is to redefine it in such a way that the biological, philosophical and religious foundations of that institution are dismantled.
Mark states the obvious and we should not back away from this lest it offends delusionists and utopians.