The whole idea of gay marriage is put forth so that gays can prove that they are normal, just like everyone else. Unfortunately they are not in a very important and obvious way. A marriage between two men or two women will not produce any children. The whole point of marriage is to provide the best possible environment to raise children. This is why marriage is given tax benefits and children are tax deductions. Our tax codes are used to encourage behavior that is beneficial to our society, such as tax breaks for business development in enterprise zones(depressed communities), tax credits for solar and wind power, and tax benefits for families to raise our next generation of children.
Of course their are exceptions, such as infirtle couples and homosexuals who adopt children, but hese are the exceptions, rather than the rules. Most homosexual couples do not have children and most straight married couples do.