1.
Oh well, might as well just destroy marriage altogether, why not, it's so far gone anyway.
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Because destroying marriage is not the right way to help people.
Please explain to me exactly how allowing homosexuals to marry will harm heterosexual marriage in any way, because I just don't see it. Also, why do you think that homosexuals are out to destroy marriage? It sounds just the opposite to me, they want to be part of it because they think it's a good thing.
2. Other than the destroying marriage argument that you are (hopefully) going to flesh out, what do you see as the most compelling arguments against gay marriage, besides religious ones?
Those who would sacrifice an essential liberty for a temporary security will lose both, and deserve neither. -- Benjamin Franklin