Churches are also, or at least are supposed to be, non-profit... which is why they don't pay taxes. You could argue, of course, the corruption in this... but in that stance you might as well argue in the corruption of all non-profit organizations or in the various loopholes that exist in non-profit tax law.
I don't agree with this, at all... I mean, I'm no polygamist... but I'd imagine a broader audience would under stand the desire for polygamy greater than that of a homosexual. Most people fall in love at more than one point in their life... so should someone hold both loves simultaneously, why shouldn't they be able to marry both? I don't mean to take a stance in support of polygamy, but I really can't see how you'd argue they don't have, or can't prove, a biological need that is pretty much innate in every human on the planet. The primary stance against polygamy is that it introduces a whole new loophole in the tax system. In reality... the same could be said for incest. The fact is, however, that there is medical reasoning for why incestuous relations shouldn't be.