The queer community and its allies needs to re-frame the debate, and the fuckwits need to be called on their fuckwittery.
Within the assumptions of Abrahamic Theism and the authority of the Bible, anti-gay sentiments make sense and strongly depend upon the notion of gayness as a choice, either of the gay person or the choices of those around them, rather than an uncontrollable product of biology. Below are what I think would be a theological response to your arguments.
i) Even if no-one were 'born gay' (whatever that means), that says nothing about that person's ability to convert to 'ex gay' (which is zero).
If gayness is either chosen or a by-product of experiences, then it is plausible that new choices can made and/or new experiences be had (conversion experiences) to produce non-gayness.
ii) Even if no-one were 'born gay' (whatever that means), that says nothing about what was "God's plan" for that person. (Also, God is imaginary).
God is the creator of the material universe and thus of human biology, and thus these inherently covey his "plan". The actions people choose are part of free will, thus do not inherently reflect his plan and can be against it. Thus, only if gayness is chosen and not biological can it be against God's plan.
iii) Even if all gays had libertarian free will in the matter of their sexual orientation (which they don't, because libertarian free will is incoherent nonsense), so what?
The so what is that it means gayness is against God's will, and therefore evil, since under monotheism, morality is determined by coherence with God's will.
iv) Can't you be satisfied that God will eternally punish the filthy sodomites in Hell? Or is She so impotent that the gays need to be hunted down while they're eking out their miserable existence before being bathed in the eternal fire?
We are here to do God's will and to shape out societies to be in accord with that will. Punishing those against his will is our duty to God. God could and will do it himself in the afterlife, but us doing it here is a kind of test of our love and loyalty to God.
v) Judas Iscariot was born to betray the baby Jesus. Jesus says so at the last supper, says there is nothing that Judas can do about it, says that it would be better for Judas had he never been born. So, there is precedent for God specifically making evil people destined to betray the baby Jesus and then punishing them for being the way he made them.
Why would you first need to establish gays were 'evil' of their own 'free will'? Gays are evil because God made them evil, and God has no problem with punishing people for stuff God did on purpose, so why do you seem to have a problem with it?
Judas is a special case, because Jesus was a special case. Judas represents creating one person born to commit one particular act of betrayal for the express purpose of bringing about Jesus' Crucifixion central to his theological role. That is much easier to cohere with the general conception of God and his plan, than creation of about 5% of the human population born to be "evil" and think evil thoughts most days of the entire life for no clear and specific purpose. This relates to the more general "problem of evil" that theologians have a hard time providing a viable account of.
Of course there are counters to these theological position and you point to some of them in your parenthetical comments. But ultimately those counters are about exposing the idiocy of theism itself, and of theistic-based ethics, and exposing the clear self-serving and ugly motives behind creating and accepting many of those theological ideas. While I agree with such arguments, the gay community is not going to go that route. Plenty of gays are still pathetic enough to be religious and cling to those identities. That is why they unreasonably deny the rather clear homophobic bigotry in the Bible. So, even if most gays aren't very religious, taking on theism itself would divide their political movement. Also, their practical political aims would be harmed by such an anti-religious approach. They are more likely to achieve social and political equality by arguing "Your God doesn't hate me", than arguing "Your God doesn't exist, so its dumb to base you feelings about me on how you think he feels about me."
