Ahhh teeth. A favourite subject of mine.
Jig's right. Many frugivores (fruit eaters) have conical canine teeth. They're useful for puncturing and holding fruit, but that's about it. They're not used in food processing.
In mammals, the food processing is done at the back of the mouth, by the molars. Fruit and seed eaters tend to have blunt, rounded cusps used for crushing food items, much like a mortar and pestle.
Grass and leaf eaters, on the other hand, tend to have sharp cusps used to shear past one another, since shearing is the best way to process tough, fibrous plant matter.
Snakes, however, have molars of no kind. They have blade-like (zyphodont) teeth that did not even come into occlusion. They were useful only for slicing through meat. There is just no way a skull like this could be used to process plant matter (the extreme kinesis of the snake skull is also terribly designed for plant mastication because it provides no resistance for pulping):
So as a YEC, you have to either admit that God did a poor job of designing the snake as a plant eater (or any other zyphodont animal, for that matter), or that all these animals underwent radical evolution post-Fall to adapt to their new carnivorous lifestyle. Either way, it's just
ad hoc arm waving.