A little help on DOMA.

I am trying to wrap my head around exactly what the conservative argument is that DOMA is constitutionally valid.

My personal belief based on some reading is that the states have the sole right to decide whether they want to allow gay marriage in a civil court. In addition, other states should recognize the union whether or not it was performed in civil court or in a church. Lastly, the federal government has no right to tell a church what to do on this issue or any other, and the constitution does not allow for a federal ban or definition of marriage.

So I am trying to find a coherent explanation from the right (for my own understanding) on why they think DOMA is constitutional. Can someone here at the very least explain their position however warped it may be?

Thanks