Gay or homosexual relationships in Nigeria has a 14 year jail term. Same relationships are accepted by the laws of some western nations. Same act, different perception and punishments in different nations.
Since same sex marriage is accepted in the USA, it means it is right in that country. If you take it to Nigeria, it is not right because our laws forbid it. Now, the big question will be what is really right since same action is right in a place and wrong in another place?
To be honest with you, nothing is absolutely right! An action is right because the laws in that place say it is. It can also be wrong if the same laws are changed in future even in the same place.
Until someone agrees to come under the umbrella of your laws, he is not bound to accept what you say is right as the right thing. So, when I hear people say that the other person's judgement on an issue is not right because he doesn't hold the same belief system and religion with them, I pity them. Christians say a thing is right when the Bible says so, Muslims believe an action is right if the Quran says so even if other religious books say otherwise.
I believe Christianity is superior but that is only because I'm a Christian that has the life of God radiating in the inside. If an atheist or Muslim see me as being mad, I wouldn't get workedout. He too also believes he is into that which is right.
I believe you shouldn't lord your opinions over others.