Good points, but I find your rejection of the idea a bit close minded.
The whole reason the Gems have to contain the gem mutants in the first place was because they instigated a conflict. I do think that what Rose did was for the good of Earth, but a war is a war. Greg even says this in The Return.
Your analogy of Rose fucking a dog is... actually pretty spot on. That's exactly what it is. She didn't even fully comprehend the concept of love, a motivation for her to give up her physical form and commit to producing a human child was her attempt at achieving a sort of... I don't know, spiritual transcendence? Like being able to experience love was her only goal? You might ask where I draw this conclusion from, and that is from the outro theme, Love Like You:
*If I could be, half of what you think of me
I could do just about anything,
I could even learn how to love.
When I see the way you act,
Wondering when I'm coming back
I could just about anything,
I could even learn how to love like you.*
There's another part I remember Rebecca Sugar added on, saying something along the lines of "I must be bad, and I know it's true, because you're so good, and I'm nothing like you...!" That pretty much spells out what I'm conjecting.
It's all very intentional. Like, if the Crystal Gems were in it just because they wanted to protect humanity, how come they never show any amount of respect or good will to humans? They seem pretty indifferent as long as nobody gets hurt, which sounds a lot more like following orders than being pationate about their cause.
No doubt the Gems care about the Earth and protecting it, but I doubt that if Rose had any say whatsoever, there would have never been a rebellion and the entire civilization would have been complacent with the complete destruction of the planet, Ruby, Sapphire, and Pearl included.
I do think Steven is good, but only because he is innocent. Naive. He does not know what it means to commit evil acts. The Gems do and feel guilty about it, this is commonly brought up, even in the Classroom Gems when Pearl immediately got apologetic over harvesting Earth for its resources.
Sorry if you thought I was trolling, but I sincerely believe this.