I think like for at least 200 or even more years gay relationships exist…and now in 21 century I have got argument for one lady that gay population is product of this century and that they should not be allowed to get married. And when I asked her why, she said: “marriage is traditionally heterosexual institution�???
I agree with you this is the weakest argument she could give you. Slavery was also a traditional institution, based on traditions that went back to the very beginnings of human history further back than marriage. But by the 19th century, humanity had generally recognized the evils of that institution, and has since made a serious effort to abolish it. Why not recognize the truth that there is no moral ground on which to support the tradition of marriage as a strictly heterosexual institution?