You have to understand the leaf-eater's perspective on this. The thumbspike was right to be suspicious of Chomper. Instinct tells her he's dangerous, and in terms of what he is, she's right on that.
Chomper is a T-Rex, who is supposed to be eating leaf-eaters. He may be cute now, but when he gets older, there is no guarantee that he'll be safe any longer.
While treating Chomper like that may seem harsh, it is justified when you see things through the eyes of a hunted. I am not saying that I don't pity Chomper. But I also wouldn't call the thumbspike a *insert bad word here* because she had reason for distrusting Chomper.
Leaf-eaters fear sharpteeth, and for good reason. They are hunted, killed, and eaten. Many likely lost their family and friends to sharpteeth. The leaf-eaters in the Great Valley may have endured countless sharptooth attacks before they reached the Great Valley. To expect them to accept Chomper after all that seems inaccurate, in my opinion. Chomper may be just a kid, but to the leaf-eaters, he's still a sharptooth.
I'm not trying to be mean, and I'm not trying to be harsh. I'm just stating my opinion on this. If you don't agree, that's fine.
And again, this is offtopic.