My point is that the definition of marriage varies by groups, both culturally and religiously. The US definition of marriage was highly influence by judeo-christian religion from Europe. Before the colonization of America, the first Americans practiced polygamy openly here. To force them to follow the christian definition of marriage amounts to violating their religious beliefs just as how other "religious" Americans find that gay marriage violates their religious beliefs.
The laws here are designed to apply to all, so its not fair for those who do not follow the Christian faith to have to put up with Christian ideologies becoming law, but fortunately due to the robustness of our legal system, we are able to correct such mistakes (i.e. ignorance).