So... am I a bad Mormon if I don't agree with the church on this one?
The problem with the government defining what is and isn't marriage is that marriage is a religious institution. It is not a legal institution, and never should have been included in any laws. From a legal standpoint, any pair of people should be able to grant inheritance rights, hospital visitation rights, joint tax returns, etc, etc to each other. If we can vote, then we are adults and should be able to chose those things for ourselves.
Marriage shouldn't be part of the government. Marriage should remain in the religious world, and then the churches can keep the definition in the traditional way that it was meant.
Can't we do that and make everyone happy?