I suppose that the image of Littlefoot's motives for the fight with the sharptooth would look less like that if they had kept the movie the original way, with Littlefoot finding the Great Valley right after the quarrel with Cera, but returning to lead the others there. At least that book which I quoted before strongly emphasizes that the sharptooth was about to find the entrance to the Great Valley.
I will not argue the point that Littlefoot is likely to have felt some satisfaction at the idea of that sharptooth finding his end, but I wouldn't judge him as harsh as you do, blaming him for risking his friend in what you seem to consider an unnecessary fight.
First of all with the death of his mother I suppose Littlefoot (even under consideration of all that circle of life stuff) had more than just a petty reason for revenge.
Secondly sharptooth was undoubtedly a thread to all of them and the choice whether or not they had to face sharptooth was not all that of Littlefoot or his friends. Much rather they just picked the time and the ground on which to meet him.
There is some good reason to think that the sharptooth was really pursuing Littlefoot and his friends. We've mentioned the story about sharptooth's eye before, but even without that one being explicitly mentioned in the movie there are some signs that the sharptooth was really after Littlefoot.
For example, why didn't he go after that herd of longneck which ate most of the leafes of the copse of trees where Littefoot and the others stopped on their way?
A single straggler from that herd would have provided much more food for the sharptooth than Littlefoot and all his friends combined. With the tracks the herd must have left sharptooth must have been aware about their presence but decided to follow Littlefoot and the others instead through very adverse terrain.
There may be a flaw in my drift of thought as the herd too may have been headed for the Great Valley and with many other herds going that way sharptooth is likely to have ended up at the Valley even without a special obesession of catching Littlefoot.
But however that may be, sharptooth was between Littlefoot and his friends and the Great Valley. If they meant to go on (and without any food around they could just wait hoping that sharptooth would go away) they had to get him out of the way.
They all knew about the risk comming from sharptooth. I really don't think Littlefoot should be blamed as overly revengeful and careless about his friends. It is not like he was forcing them on a revenge campaign against sharptooth chasing him all through the Mysterious Beyond. Sharptooth was there and would have been a peril to them and the Great Valley even if Littlefoot had been very fond of the poor creature who just followed natural instincts, set by a cruel biology, when killing his mother.
I don't think that we should expect Littlefoot to be remorseful over sharptooth's death, yet I do think that one could expect some more inner conflict on Littlefoot's part whenever he is dealing with Chomper.
