If nobody else will answer this, then I will:<quoted text>
And I ask: What gives us the right to restrict the number to "one" ?
Our right to limit marriage to one person is backed by the fact that no stigma in our psyche rationally provokes us to want to mate with more than one person. Maybe on a conscious level that may seem like the case sometimes, but it doesn't resonate subconsciously, or at least has not yet been shown to by psychologists.
Which is exactly the opposite case for homosexuality. Scientists, biologists, psychologists - they've all reached the same conclusion regarding this. When it's looked at in an objective, unbiased light, any experienced practician can see the trend: homosexuality is just as genetic as taste buds. The desire to commit bigamy is not.
Gay relationships are not the equivalent of bigamy and shouldn't be equated as such.