Funny

Fine, we'll put aside the accusation of solipsism for a moment and come back to this:

By the same token, there's no way that you can prove to me that you understand personal mortality. If, for the sake of argument, I were to point a loaded firearm at you and you were to attack me, attempt to flee, beg for your life, whatever, there's no way you could prove to me that your actions are motivated by a subjective will to not die: for all I know you might just be acting very convincingly like someone who understands mortality without actually having any interiority whatsoever.
However, there is social utility in assuming that others are capable of understanding abstract concepts when they perform actions in accordance with such an understanding. And from the fact that most animals will try to avoid things that they can reasonably understand will cause them death (natural predators, environmental hazards, anything that has caused them injury), we can likewise extrapolate that they don't want to die.

You'ven't made any meaningful rebuttal of anything I've said here. This is why it's easy to assume you're arguing in bad faith: I'll clearly state my position and explain my reasoning, and then you'll just come along and hit me with the "nuh-uh," and refuse to elaborate. At my insistence that you justify your own position, you've so far given me "but different things are different," and "but it's normal tho."
In the case of the former, I have explained why in the context of this discussion the different things are actually quite similar in the way that actually matters here. And given that you appear to hold sincerely leftist beliefs on every topic except animal liberation, I really hope I don't have to explain to you how "but it's normal tho," has been used to defend countless atrocities, historical and present, and as such I shan't accept it as a justification.