Not only can it not be changed because it is revealed by God. But also because to try to change it is like marring a painting God has made of Himself for us. When the beloved hands you something saying: "This is me." Who takes it and says: "Oh I love it and I love you...but your ears would look better like this..." and just starts changing it?
God is perfect in her ethics and her love. So, it naturally follows that she would not ask more of us than she asks of herself. The Incarnation is symbolic of that- where God became human and had to deal with the daily hardships of humanity, and ultimately a brutal unjust execution.
When people who seek to reform dogma and doctrine are thought of as not loving God for who she is, and there is the assertion that this is therefore a manifestation of imperfect love, because you don't only love someone on the condition that she change, you love her unconditionally, then surely the same morality would also be applicable in reverse- that God must love and accept us for who we are, unconditionally. And, of course, that means no eternal torment, no telling homosexuals they can't love who they were born to love, etc..
Except... that last sentence would violate a doctrine or two, wouldn't?
So, isn't it possible that we should question and seek, and combine the wisdom of our ancestors in faith with an evolving ethical understanding of what love is, and who the God who is a reflection of perfected love is?
Jesus taught us that we are not to seek an eye for an eye, but to turn the other cheek. Surely, God herself does the same and does not condemn people to an eternity of torture- she would turn the other cheek and not say "Do as I say, but not as I do". The God who the Church teaches condemns a finite amount of torture as inhumane, itself a position that has evolved for the better since times when Inquisitions and such were sanctioned, could not simply then turn around and sanction eternal torment. Justice is not served by infinite punishment for finite sin- not even Old Testament justice, which said to put aside taking more than you lost, and simply balance the scales, an eye for an eye instead of a life for an eye. God must walk the walk as well as talk the talk- I don't always live up to that standard, but then, I'm only human- I don't claim perfection. God does.
Our ancestors in faith who wrote the bible, feeling inspired by God, who then had their writings received as sacred scripture by the larger faith community, got that justice is no more than equal punishment for equal crime, and then evolved that even further, advocating that love be shown to those who hate us. Those writers and communities may not have immediately been able to process or accept the true implications of their revoltionary ideas, but as St. Paul admitted in an epistle, we see God but through a lens darkly and are constantly wrestling with our salvation.
We grow and and build and evolve, and perhaps one day our distant descendants will stand at the top of the pyramid of knowledge of love and ethics, and touch the true face of God as she is. Or maybe we can never fully comprehend, but will ever progress forward, with a step or two back here and there, but ultimately with forward monetum, growing ever closer to the infinite until we are one with the stars and the heavens and the songs of angels.