This is a minor technical point that distracts from the main discussion, and doesn't really support the implication from your earlier comment that some gay people are against gay marriage rights. Saying method 2 is better than method 1 is not the same as opposing method 1.
What about outright opposing Method 1 because you don't think the Ends justify the Means? Even if you agree with the Ends? Even if you like Method 2?
I'm my experience, that gets me branded as a monster. I tend to keep my mouth shut.
The implication does not exist unless you want to put it there. I even added a second, longer sentence to emphasize that being against a particular law is not the same as being against gay rights. The fact that you insist the implication is there despite all that is precisely my point.
No adult should have to seek permission from government to form, codify, or have a relationship "recognized"
At most you should be required to file civil contract declaring a partnership has been formed between 2 or more adults, what the terms of that partnership are from a financial and property stand point, and should include a disillusion process.
That is a radical shift from what we have today, but "Family law" is a complete mess and needs to just be completely abolished and replaced with Voluntary Agreements and Civil Contracts outside the control of government.
The sexual organs don't have a pre-ordained purpose. The argument falls apart at the very first premise.
If the actual concern is that all of humanity will turn gay and then we will go extinct, well, it's safe to say I'm not too worried about that.
The parent's point about philosophical literacy is apropos here. Natural law and its underlying metaphysics is very technical and deep. It is definitely not falling apart by pointing out the obvious, that biology varies over time. In some respect, NL has dealt with that "problem" since the time of Aristotle. (For a start: https://plato.stanford.edu/entries/essential-accidental/)
This may be true, but such endeavors must reconcile with modern scientific understanding one way or another, or they can lose validity/usefulness. I haven't seen any convincing efforts to do so.
Note, this would be less of an issue if they didn't make certain specific claims or rely on certain specific premises that the natural sciences directly touch. E.g. the "purpose" of sexual organs.
One relevant idea that has been growing stronger for me is that a philosophical endeavor needs some sort of strong, tangible connection to reality in order to have meaning or usefulness. Without such grounding, it is far too easy to end up with something that seems reasonable on the surface but may actually be nonsensical or illusory.
Important: disagreeing with or opposing a gay marriage law is really not the same as being against inclusivity, diversity, or gays. Some people will have both traits; the problematic (for lack of a less polite word) one is the latter, not the former.