Government for the People or People for the Government?

I was told that heterosexual marriage benefits the government by providing the government with a next generation of children while a same-sex marriage would not. This was given to me as a reason that same-sex marriage should not be legal.

While it is true the government can’t produce for itself children we must remember:

People are not for the benefit of government; government is for the benefit of people. A government is instituted to provide for the protection and well being of the people, and to insure that the rights of people are not infringed.

Therefore a law limiting the rights of people cannot be justified on the merit that it benefits the government.