I’m just an ex-Mormon agnostic atheist, and you’re absolutely right, and trying to say that the hardliners are not “Christian” is overlooking a well-established tradition of Christianity being shitty. They are perfectly within “scriptural authority” as they understand it and as their ancestors have understood it.
On the other, there is room in the historical record and scholarship of the Bible as historical text to make a case for an evolving faith that can forge a kinder path, and I think many of the remaining protestants in Europe and “mainline” Chritian churches in America try to to this to one degree or another. Unfortunately, they are all much too content either to humor the fundies, maybe because many in their own congregations would pick that theology if forced to choose explicitly, or else they “No True Scotsman” the hard liners and count themselves done with it.
If you are a Christian who believes that your God is kinder than he is described, then assert that confidently. Make a place in the world. Assert that your Bible is a flawed documentation of an evolving faith tradition. If you can’t do that, and most of them can’t because they fear the Southern Baptist Convention might be right, then you have to live with being conflated with those who think Iron-Age nonsense and cruelty should be the basis for a modern society.