Oh, for heaven's sake: a man has a dick, and a woman has a fanny. The former fits, and is meant to fit, into the latter. Two men have to make use of the rear entrance, and two women have to use dildos. Is that clear enough? That does not mean that relationships can be reduced to the physical: two men, or two women, can have a loving, faithful, life-long relationship just as much as a man and a woman. However, since it is not the norm, I don't think it is a good idea to have gay marriage, and it isn't necessary, since civil partnerships give the same legal protection as marriage.
Floo - what entitles you to speak for gays?