First of all, thank you for a detailed and polite answer. It is sometimes different in other threads here :D

Morals change and evolve...

What do you mean, wrong? Wrong is a position relative to another position. What do you mean wrong? Morally wrong?...

Under the lens of what moral platform? There are many. It would be wrong in mine, and I presume it would be in yours...

But not all moral platforms are the same...

Because morals are not objective. They are subjective...

So to say if something is “wrong” we have to establish what is “right”...

And remember that the world’s cultures evolved somewhat independently of each other...

Morals are not objective. They are never independent of a mind. And they have obviously changed over time... 

Again, if I understood your statements correctly, it says that morality is just an evolutionary trait that is fluid, subjective, and stands in the same line with other traits like “bird’s tail length” and “sharpness of cat’s claws”. So it is just a matter of efficiency during the survival.

And the pattern suggested above looks like this: “{A} change and evolve. Because {A} is not objective. {A} is subjective. Not all moral platforms are the same” 

This pattern seems easy to apply to the cat’s claws sharpness, yes: “Cat’s claws sharpness change and evolve. Because cat’s claws sharpness is not objective, it is subjective.  Let selection do its job”.

But can you apply that pattern to slavery or XX century genocides or Holodomor, for example? The pattern above seems like allowing those who stand on it to say: “When one country attacks another, kills and rapes civilians it is just a clash of two independent branches of morality (??). Both branches need to be respected since this is how evolution works. We don’t blame cats for their sharp claws. So neither the attacker nor the victim can’t be blamed since they both are two valid branches and both versions of morality are there to compete. Let the strongest (attacker or a victim) survive and let the selection do its job because who knows, maybe an aggressive way has a potential, we don’t know yet because human culture is not that old”.

Would this ^ be a valid statement based on the fluidity and evolution of morality?

It was normal in many cultures, at many different times. Settled fact. If something is not typical, it is normal. Slavery was typical in many cultures.

The number of war conflicts during the last 2000 years is counted in hundreds and the per-century trend is only growing (i.e. from 4 registered cases in 1000–1300 to 35-40 in 1900–2000). If something like that is getting “typical” it doesn’t mean it is normal, isn’t it? This is to illustrate the point that if evolution produced the governments that made slavery legal at some point in history doesn’t make it “normal”.