Apes always being racist and angry towards humans makes no sense

It's plot hole in all movies. We are always being shown how Apes hate and despise Humans because humans treated them like slaves and were hurting or some shit.

We always have that moment. When at some point ape fins some stupid children's book where Oh HORROR - some monkey sits BEHIND BARS in zoo. And apes are like: "YOU MONSTERS!!! All of you, humans. We can't treat you like equals because you will enslave us all again and put in cages!"

It's always looks stupid because who actually goes to zoo to see monkey. They go to see lions and Giraffes. Not to mention that very small number of apes are in zoo. Majority of them live their free life in jungles.

But movies always imply as if apes were slaves of humans.

Now plot hole is that movies always show how apes are kinda stupid and don't learn history and are being surprised when they find that obligatory "children's book about zoo". They actually don't know anything about humans and past life. And those who might know - some wise orangutans - hide it.

So apes have no reason to hate and despise humans. For them they should be like some monkeys or stray dogs for us. Like they are some brainless animals who run around.