I expect not even a majority were to the point they were unrecoverable.

So they're not unrecoverable, but we still shouldn't treat them like humans?

Really? This is where you want to take it? There's plenty of scholarly discussion about dehumanization (particuarly surrounding WW2 and the events leaading up to it)....

Here is something I found after a quick search (I'm sure there are better examples out there. Hannah Arendt is a good place to start):

https://www.cambridge.org/core/books/abs/anthem-companion-to-hannah-arendt/explaining-genocide-hannah-arendt-and-the-socialscientific-concept-of-dehumanization/9F5785E91D0742BD3429D7B1933156F1

This, the authors tell us, is an example of dehumanization. The doctors fail to recognize their shared humanity with the prisoner: they fail to empathize with their victim, which leads them to disregard his suffering, which in turn enables them to treat him in ways they would otherwise have deemed morally abhorrent.

The concept of dehumanization has assumed a prominent place in socialscientific thinking on genocide and mass atrocity. It has been called a “master category” in discussions of mass murder (Goldhagen 2009, 319) and “a chief premise in scholarly accounts of the Holocaust” – the “sine qua non” of such “large- scale evil” (see Vetlesen 2005, 93). Many scholars see dehumanization as a necessary precondition for genocide. Sociologists portray the diminishment of the victims’ human status as a “prerequisite to their destruction” (Alvarez 1997, 168).“ Without dehumanization,” historians argue, “the murderers could not have committed their crimes” (Blatman 2011, 424). The president of Genocide Watch has declared dehumanization one of eight universal “stages of genocide” (Stanton 1998) and psychologists confirm that “no mass atrocities in the contemporary world have occurred without some form of dehumanization” (Kressel 2002, 172).

I was going to copy/paste more before realizing I was just copying the entire page. I highly recommend you just read the thing yourself.

Nothing good ever comes from dehumanizing people.

Regarding your argument about other animals... I just... I don't even know what to say. We are talking about humans being viewed as less than human. Has nothing to do with treating animals like people (which is also something we shouldn't do, but for completely unrelated reasons).