Actually, homosexual orientation is not well understood; that there is homosexual behavior in humans sure is.
But that aside, for most of the history of humankind, race was not understood, either. Evolution wasn't even known. Would that have warranted punitive measures against interracial couples, in your view? Bans on interracial marriage?
OK, so sometime in the past race was not understood and racial bigotry was common.
Now we do understand race and racial bigotry is not acceptable.
Today we do not understand homosexuality. Baseless bigotry as a behaviour is no longer acceptable but it does not follow that measured scepticism about something which we do not understand is unreasonable.
I am proposing that homosexuality is something that we are still warranted in being sceptical about since we really do not understand its cause or function.
That fails to address my questions. As I mentioned, for most of the history of humankind, race was not understood, either. Evolution wasn't even known.
7. Would that have warranted punitive measures against interracial couples, in your view?
8. Bans on interracial marriage?
By the way, race is not as well understood yet as you some to think. You say "Humans are adapted for their geographical location which is why they look different racially." But that may only be part of the picture. Are you sure that factors such as drift or sexual selection didn't play a significant role?
But in any case, you're right that in the past (even today) racial bigotry was common. But it was still
immoral (even if, perhaps, it's even more immoral today, at least in context in which more information is available, and all other things equal).
The point is that not knowing what causes racial differences didn't warrant punitive behavior against interracial couples (for example).
Now, you say "I am proposing that homosexuality is something that we are still warranted in being sceptical about since we really do not understand its cause or function."
But that's not all or most of what you're proposing.
You're proposing, among other things:
a. To take punitive action against homosexual couples - regardless of the orientation of their members - who display affection publicly in the way heterosexuals couples do.
b. To change the colloquial meaning of the word "marriage" to exclude homosexual relationships (well, you see it in the opposite direction, but you just ignored my arguments in support of the view that the word "marriage" in English already refers to some homosexual relationships, and the linguistic evidence that supports them).
c. To keep the legal meaning of "marriage" in Australia unchanged.
d. To ban male gay couples from joint adoption - which they're already allowed to, in several parts of Australia -, or perhaps to list them as less good for adoption or something like that, and only allow them to adopt if there are no straight candidates (what you actually propose is not clear, but it's clear that it's quite restrictive).
e. To ban or restrict adoption by single gay men, to an unspecified extent.
f. Perhaps (it's unclear) to ban joint adoption in the case of lesbian couples, and/or to restrict adoption by single lesbians.
If you were only proposing remaining uncommitted on the issue of whether homosexual orientation - not behavior - is always a sort of malfunctioning or illness, perhaps you would not have faced arguments debunking your claims - though you would still have found many committed opponents. But you're proposing a number of punitive or at least right-restricting measures.