I’m not trying to be rude, but the OP may want to do a search about this topic on this very forum (& in Social Justice). There have been several threads about it even in the last 3-6 months. Also several threads in Political News, and possibly some in Moral Theology. After you read some of the arguments there, you may find some common ground with others.
Bottom line: Not all anti-gay-marriage argumentation is related to religious principles. Much of the opposition is social and biological; some of it is practical. Plenty of atheists are against gay marraige; plenty of
gays are surprisingly against gay marriage. I’ve stated the reasons for my own opposition to it, as has benadam, as has Enchanted Eve, and at least 1 or 2 other people who similarly stick to non-religious arguments.
The religious argument will never hold in the broader, secular U.S. public, any more than religious arguments against abortion will. If you aim to win battles, let alone wars, and you do not share a common perspective with the opposition, you have to find a common perspective and common (non-theological) language in which to communicate. Otherwise (as with abortion) you will get this:
:banghead:
So I encourage the OP to search the threads and then return to seek further engagement about it.