I'm still trying to figure out what word that is.
I know I use common speech all the time with my stories, but that's mainly because it's almost impossible not to. Just about every scene in TLK has at least one reference to human culture, in one way or another.
What is important isn't the words, as much as the context in which the words are used.
In DGFone's example, even though Simba is saying the word 'man', he isn't actually referring to the human race. 'Aww, man!' is just an expression of disappointment. If he said 'Aww, lion!' instead, it would have sounded incredibly weird, and that unexpected weirdness would almost detract from the immersion of the scene.
I'm pretty sure the editors saw that mistake, but chose not to correct it. For literal expressions, it is very important to make sure the language makes sense, but for figurative phrases and expressions, it's hardly relevant.
Consider this. As humans, we don't have tails, but sometimes we'll say things like 'he's on your tail' to mean that you're being chased or followed. It's the same concept, just in reverse.
Now that I think about it, I think I know what that word is. As weird as it would be to read that in a Lion King fanfic, would it really make sense to replace it with another word of the same meaning? There's an entire plethora of colorful words to use in the English language, to describe jerks.
The question is, who is using such a word, and why? It's not the terminology itself in question, so much as it is the reasoning behind it. I can't imagine any of the characters using the word, except maybe Kovu, in an informal context. I'm sure he learned a few expletives at a young age, growing up in the Outlands with only one parent.
(<-- how ironic XD) ) and these fics usually focus on these characters. That's not to say they're all bad though, it's just a lot of them are very 
