Change is the only constant? When is it or has it ever been morally acceptable to rape and murder an innocent one year old child?

Sadly, for thankfully brief periods among relatively small groups of morally confused people, this happens from time to time. They would likely tell you it was morally required, not just acceptable.

https://en.wikipedia.org/wiki/Nanjing_Massacre

https://en.wikipedia.org/wiki/Wartime_sexual_violence

Looks like someone just discovered philosophy... I wish the world were as simple as you seem to think it is.