Hi. Member of a cult here (at least by your definition). (Well, and we're all members of a cult by Webster's definition.)
"There is none good but God."
I can't say how "the cults understand" this. I am not a cult. I am just a person who
you define as a member of a cult. So I can only speak for what this means to me. I am actually not a "member" of much of anything (see user name) but I guess I'd fall into the "cult" category for you because I don't agree with you and I am best described as a Christian Druid (Christian by faith/practice, Druid by philosophy/practice).
I believe this is saying that all goodness comes from God. So everything that is good, is of God. God's immanence shines through to us in all good things on earth. Christ was saying, "Look, all the goodness you see, including the goodness in me, is from God!"
If you are saying that there is nothing good on earth, then you are limiting God. You are putting God in a "non-earth" box. On the contrary, there are lots of good things on earth, and these point towards the immanence and goodness of God. This is why the Psalms say that the heaves show God's presence, and why Paul says that all humans are without excuse (in their choice whether or not to seek after God) because even if they have not heard the gospel, they have the Creation itself to speak of God's presence, goodness, and love.
When we are good to others, when we love others as we love ourselves, we are also showing God's immanence. This is why this commandment is so important. We can show Christ's love to others by exercising the goodness of God that is in us.
I believe Jesus was a pure manifestation of God. He completely emptied His human self (desires, fears, etc.) and was, at the end, entirely filled with God's love and spirit, though in the form of a man. He was not only God, but also man, and this is how He unites the two. That He struggled as a man is Biblical, down to His time at the Garden before His cruxifiction, when He asked God to spare Him.
That said, I do not think we are saved by Christ's blood sacrifice, per se. Christ is an eternal essence of God; He has always existed and will always exist. Jesus was the temporary manifestation, the personification, of this essence of God's grace and love and pure goodness, into human history. Christ's sacrifice (God's sacrifice) has always been and will always be. His sacrifice was not simply cruxifiction on a cross, but much much more. God's sacrifice is His willingness to love us despite our sins, His grace in the face of our cruelty and self-centeredness. A lot of humans (of all cultures and religions) couldn't really understand the extent of God's grace and love. And so Christ was made manifest in Jesus (the man) to show us the extent of God's love for us and to give us a guide for how to lead a life truly pleasing to God- a life that is free from "the rules" but following the right path, leading us to extend God's love and grace to others in turn.
So I suppose I fit in an odd category for you. I believe in the perfection of Jesus Christ, and His rightful place as an essence of God. But I do not believe that God demands blood sacrifice, so I think to see it in that way is limiting the true Gift that was given. Yes, there is none good but God. But God's goodness is in everything He ever created, as Genesis says. We can choose to not be good (that is our free will), we can choose not to cultivate the immanence of God in us, but we cannot be totally rid of it. We can only ignore it, and even this is only finite, for we exist in mere slivers of time and understanding that are as nothing at all to the eternal God.