You're right, but it's deeper.

We define morality based on the idea that you follow what God told you. It's a very old idea. Even before we had one monotheistic god, morality was still defined by what the gods of various things asked. If they asked for sacrifice for the harvest, it was an honor to give it (this is the story of Abraham and Isaac, btw). If they asked for you to worship at this time at that temple, you did it out of fear the rain might not fall or the sun might not rise again the following morning. So, the priest class which set itself up as the messengers of the gods' will became able to control society accordingly.

If you're a believer of Christianity, you believe in the 10 Mosaic commandments, the commandment from the Garden of Eden not to do evil, and that the ideal life is one following the example of Jesus of Nazareth.

Satanism is about rejecting all of that. Most simply stated, it's about rejecting God (or the gods, as interpreted by the priest class) as the arbiter of what is right and moral and inserting yourself. God doesn't define what's good and bad. I do. So, whatever God says to do, I can either go along with if I want, or reject it if I want. If I want to lie, I'll lie. If I want to kill, I'll kill, etc. It's not immoral because I don't believe in God's commandments or that He had any right to command me in the first place. I believe in my own commandments based on my own judgement. And, the rules can change, because I said so.

Take a step back from that logic and you'll see that Satanism is about declaring oneself to be a god, rather than some mere weakling or servant of God. Another word that gets used is "humanism," but it's still just this idea. I make my own rules. I define morality, not some god. (This is also why you hear "live your truth" all the time now. Same idea.)

This is why you see the embrace of science to change the rules. Why do they push abortion? Because you can use it to defy God. A woman doesn't have to make life if she doesn't want. She's not a baby maker like in his "plan." Why do they push homosexuality? Similar concept. Man is not constrained to only have sex with a woman and only for the sake of being fruitful and multiplying. He can have sex with whoever he wants and damn the kid. If he wants to bang another man, he defines his own morality. And transsexualism is just another example but more extreme. A man doesn't have to be a man simply because God made him that way if he doesn't want. He can give himself hormones and mutilate himself with surgery and be a woman if he wants. God doesn't dictate the trans-woman's reality. "She" does. There are no rules. Those rules are just a made-up set of rules some old priest came up with and attributed to God so he could control you and impose his own will on you. My rules are my own. See how this works?

When they say transhumanism, it's essentially this same idea - that Man, through his own ingenuity, can become whatever he wants. He can exceed the restraints God put upon him, because he is not merely God's "creation" as a servant like the animals. Man transcends all that with his will. He's not constrained to follow God's plan or God's design. He makes his own. Man is, himself, a Creator (a "God")!

That's what Satanism is about, and that's what ultimately underlies these movements.