Whatever you want to call them - do you think that they would not be entitled to, at the minimum, a right to life to the same degree as humans (i.e. killing them should be treated as murder)?
Only if they can fight for them. "Our Creator" didn't endow man with the rights to life, liberty and the pursuit of happiness: men fought other men for those rights.
"Wait!!", you say. "Babies and Down's Syndrome people, and people in iron lungs can't fight. They must not be human, either!!" To that I reply, "They came from humans, so must be humans."
but not all humans have 23 chromosomes
You ignored the other differences.
Interestingly -- and off topic -- males with DS have never been known to reproduce, and only 1/6 to 1/3 of DS females are fertile.
Ultimately, all this is just accumulated mutations and selection of them over the course of that 6 million years of divergence.
Why stop at six million? Why not regress back to 90 Mya and the first placental mammals? Or even further to the probainognathians, cynodonts, synapsids, amniotes, chordata, animalia, eukaryotes, bacteria, all the way back to the Last Universal Ancestor? Call everything human.
If you could incrementally edit a chimp's genome to make it human, at which point during the process is it "human enough"?
I don't know that.
But we do know that if it comes from the joining of male & female DNA, then it's human. And that's Good Enough.