Today i had a "separation of church and state" discussion with my religious mother...

Essentially, we were discussing gay marriage and she was saying that it's a sin, etc, and should not be allowed by law. She also claimed that legalizing gay marriage would negatively impact the economy because married people pay less taxes and such.

I didn't really know what to say- I know the bible is very clear about the whole thing, but the government is no place to enforce religious matters. Then she started talking about the US of A being founded as a Christian nation and how we're getting away from that and such.

I just sorda moved away from the conversation because I don't care for arguing with my mother.

What I'm asking is one, am I incorrect? And two, how should I go about discussing the matter without being all aggressive like I feel most of these types of discussions are?