Should we make omnivores the villains?

I don't mean Ruby, as she's good, but seriously, the fact that Sharpteeth spit out Tree Stars and stuff might give them a cop out for killing stuff.   However, what about omnviores (i.e. those that CAN eat Tree Stars but might want to eat, say, Cera, instead)?   Seriously, this would be interesting to have such dinosaurs in there.  There fun part of this is that it might give me a cop out with Chomper.   Create these evil omnivore types, have them try and harm the Great Valley and plan world domination (becuase they think their diet makes them superior or something like that), and then have them get foiled, and Chomepr decide to hunt THEIR kind.   Then Chomper can go after a group that we don't like and he won't have to hurt our beloved Flatteeth.