Let's face it, there are three Talking Sharpteeth:
1.) Chomper
2.) Dil
3.) Ichy
Dil does appear to have some family (Ichy mentioned Dil's father in the song Who Needs You?) yet Dil never mentions Ichy's family at all (not even to try and insult him back.) The fact that he can talk also seems to suggest that he may have had some contact with Leaf Eaters (other than as food!!!!) in the past. True, Dil can talk too, but something Ichy says makes me think HE may have been the one to be a former Friendly Sharptooth. He refers to the kids as "animals". While this may just be coincidence, what if it's not?
What if Ichy was friendly with herbivores, but had some falling out, then having once seen them as sentients or whatnot, finds them as food, but, feeling guilty about such, convinces himself that Leaf Eaters are "animals" to dehumanize them.
Ichy could be a view of what Chomper WOULD HAVE BEEN had he gone bad. (Note: I plan to get Dil and Ichy redemption.) Thus, Chomper could ultimatley be nice, but Ichy can be a view of what he could have been, thus pleasing both those who would have wanted to see Chomper go bad and those who want him to stay nice.
(You have to admit that, at any rate, if Chomper goes bad, his life is likely to tend the direction of Ichy's life, not a pleasant one, even by Sharptooth standards.)