You say you want to see Atheists playing a bigger roll in the Republican party. At the moment you are an infinitesimal part of the GOP.
Have to start somewhere. Atheist organizations suppressing atheist Republicans doesn't help.
I don't think the Secular Coalition for America has any responsibility to print your article especially when they don't agree with the premise.
No, they ultimately do not have to publish it. But they said they would publish something so I consider this to be bad form. They could have written their own piece.