Yup, you're absolutely right, the 50% of heterosexual marriages that succeed in this country are definitely better for children, not to mention the scores single parent families arising from heterosexual couples.
If the parents are committed to each other and the family, why do you care?
How is it "wrong and damaging from a societal standpoint?"
If you had said you just don't like gays and think that they're icky, that's a valid opinion, silly and juvenile but an opinion you're entitled to.
If you agree to the logic of this article, then why don't you have a referendum in every state. Homosexuals can vote for whether they want the ability to marry or not. If you're heterosexual you don't vote because it doesn't affect you. Then see what the results are.