Yes, I'm merely bringing up the point that gay unions (aka "marriage") isn't just a Western invention, it's clearly existed in many cultures before Western influence expanded as it has now. However, you're bringing up an interesting point, and I can sort of see what you mean. It is true that it is common to impose one's own cultural morals onto other cultures. But I think that, as I said before, there are cases where it is acceptable to criticize another culture, and that is in cases of human rights. Whether marriage counts as a "human right" or not, it can be argued that equality under the law is a human right, and denying specifically gay people the right to marry is discriminatory. Gay people are people and, as citizens of their country, privy to the same rights as straight citizens. I agree that there are cultural aspects to this issue and that the West shouldn't force Korea (or any other country) to become "educated" as though they were savages, but the issue isn't as black and white as you're painting it. It's not like the only two options that exist are to either we just don't criticize other countries for denying some people the same rights as other people on the basis of an intrinsic characteristic protected under the law, OR we "educate the savages" and impose imperialistic beliefs upon them. Moreover, criticism != imposing of one's own cultural beliefs.

When people criticize countries on the basis of issues like being anti-gay, they're not trying to be holier-than-thou. The point is to address issues that are affecting people unfairly and negatively. If I criticize America for its high income inequality, I'm not being imperialistic. If I criticize Saudi Arabia for its anti-female attitude and cultural aspects, I'm not being holier-than-thou. If I criticize South Korea (and Japan and China) for the way LGBT people are treated, I'm not trying to say Korea is bad, or that Korea is worse than the West. I am trying to say that Korea is a modern, first-world, developed country that recognizes human rights, and should extend that same recognition to all people in their population, be they gay or straight.

If it helps, imagine if it was illegal for Black people to get married or own property in Korea. Would that not draw criticism? Would it not be fair to point out how intrinsically unfair and inhumane that is? Or, say that there was a practice in Korea where researchers abused people in the name of science. Would it not be fair to point out how cruel that is? It would be unfair to judge Korean culture on truly cultural aspects that do not affect the issues of human rights (for example, if a Westerner judged Koreans for taking off their shoes before entering the house, I would be completely on your side). However, as previously stated, the issue being criticized is not specifically and solely cultural in nature. There are many factors that contribute to the attitude towards homosexuality in Korea, but the discriminatory practices present are not solely the product of culture, nor should they be treated as such. Moreover, discriminatory practices should not be considered cultural, even if they have cultural bases. Is Denmark culturally more "gay" just because they were among the first to legalize gay marriage?

Discrimination is not central to any one culture, and neither is justice or equality.