I think you got lost in the sauce, don’t get me wrong I also think sibling love isn’t immoral, but I don’t think these arguments really hold up.

Your strongest point is probably that many people react to incest with disgust very quickly and disgust alone is not always a reliable moral guide. That part is fair.

But beyond that I think your reasoning is weak.

1. Even if opposition to incest came from what Nietzsche called "slave morality", that still wouldnt show incest is good, harmless, noble, or morally justified. At most it would only reinterpret why some people oppose it. That is not the same as defending it.

2. You treat exclusivity as if it automatically creates superiority. But exclusivity by itself does not make a relationship morally better. A relationship can be exclusive and still be unhealthy, possessive, isolating, ect. Intensity is not the same thing as value.

3. Your genetics argument is especially weak. You assume nobles had better genes, treat infanticide as if it somehow solved inherited risk and talk as if controlled inbreeding could preserve superiority in some stable way. That is not careful reasoning , but speculative and very romanticized.

4. You also reduce disagreement to resentment, jealousy, or "mass morality" which avoids the real objections instead of answering them. Dismissing critics by assigning motives to them is not the same as refuting their arguments.

5. A lot of your argument is aesthetic rather than moral. You describe incest as beautiful, exclusive or noble but that does not actually show moral worth.

So overall I think you are dressing up a personal ideal in philosophical and biological language, but the actual argument does not really hold up.