Hi noname!
Interesting! Really interesting an interpretation / analysis. It's a pleasure to read such well-thought out an essay!
I had never really realized that remark of Shorty about Bron ignoring everyone. In general I have a rather low oppinon of Bron, for reasons I mentioned already. It's also interesting to see that, while his herds seems to be so dependent on him that he can't go to the Great Valley of his own, he didn't hesitate to leave his her behind to go to that crater (why didn't he bring his whole herd along?).
The thesis of longnecks in general being a very arrogant species sounds quite surprising, but the points you came up with leave little room to discredit the thesis.
I think we can take it for granted that the creators of land before time don't mean to let longnecks appear arrogant or something. And despite the points you found there are also many positive points in the movies. For example you don't see longnecks use their size or strength to suppress others. On the contrary they seem to be much more peaceful than the other kinds and it takes a good deal of provokation work to get an angry remark from Littlefoot's grandfather, who often takes sort of a mediator's role (e.g. in LBT 3).
I find it somewhat difficult to accept Littlefoot's attack on Cera in the original movie as a counter-argument, for one really has to admit that he is in an especially tensed emotional situation. Also note that he accepted many other provokations from Cera without showing much more than a frown and that he helped her secretly (so he didn't do it for the recognition it brough him) when Cera insisted to get her leafes herself in the original movie.
I do agree so that in general many of his reactions are more based on emotions than on the mind which (honorful as his emotionally based actions are) doesn't make him a perfect leader. I think Don Bluth himself wrote something to the same effect.
The fact that Cera's father is especially after Littlefoot with his anger may indeed show a strong rivalry between threehorns and longnecks. Flyers or Duckbills may be considered no "match" and thus not be minded as much. In fact Cera's father claims Duckbills to be stupid in LBT 5. There IS by the way a clear indication that Littlefoot is not the only aim for his anger. In LBT 2 Cera apparently quotes her father by enumerating the kinds she mustn't hang around with, which includes Ducky's, and Spike's kinds too (while flyers aren't mentioned). It may be that Littlefoot is partly so much in the focus of attention simply because in a way he is THE maincharacter of the land before time.
As for the execution of the sharpteeth through Littlefoot's grandfather and Doc, I assure you that it must've been that way (I'm the one who most frequently complained about that scene). From the look of It Dock and Littlefoot's grandfather must've pushed the unconscious sharpteeth to the bottom of a rocky pinnacle which they make collapse above them with their tails.
