That's true. I cannot explain how it causes hunger in Africa. Or how it causes global warming either. That doesnt mean those things have ever been arguments against "gay marriage." I can tell you that defining marriage is a state power which is being undermined by an activist judiciary. I can tell you that gay marriage is poor public policy because it undermines the purpose of state sponsored marriage to begin with.
The only arguments against those two are Arguments 1 and 2.
You may tell anyone anything you like, but it remains subjective opinion and factually wrong.
The issue has nothing to do with 'defining' marriage; indeed, all parties involved agree as to the definition of marriage and in no way seek to 'redefine' it.
The issue concerns the fact that same-sex couples are eligible to enter into marriage contracts in all 50 states, where some states seek to deny gay Americans access to marriage law in violation of the 14th Amendment.
Americans are citizens of the United States first and foremost, residents of the states subordinate to that, including gay Americans. Citizens' civil rights as guaranteed and protected by the Federal Constitution are consequently immune from attack by the states. As a fact of settled, accepted, and fundamental Constitutional jurisprudence the states have no 'authority' whatsoever to 'decide' who will or will not have his civil rights.