Every single one of us is an ape. One can't be a human if one isn't an ape. Therefore to claim that someone isn't an ape is to deny them their humanity. Actually it is saying they aren't even closely related to us.
Eh, at which point you demarcate between categories is pretty arbitrary unless you can show certain relations between those categories that emerge with the new demarcation that can be generalized in some useful (vague term here) way.
To me, what's an even more fascinating question is why can we understand language (and articulate, with visual/auditory symbols) but apes and other creatures can't. What is the mechanism that prevents them from doing so.