Of course once the population is under control then this may no longer be just because of the disadvantage of letting them be extinct and never being able to enjoy rabbit again, and the disadvantages of their large numbers not existing anymore..
I think we continue to disagree here. I personally have a lot of affection for all animals and I would have to be a vegetarian if it were up to me to kill my food. However I don't think that "justice" is involved here, and certainly not any kind of weighing "extinction" as some kind of duty to nature or to rabbits in general. I definitely think that a strong case can be made for me and others like me who agree to band together to defend a population of animals to prevent them from going extinct, even at the cost of inflicting some pretty strong harm on the humans who disagreed. I think we see this kind of conflict going on now in parts of Africa in regard to animals such as elephants, but that's just one example of many and probably a poor illustration.
So I hold up my credentials on cruelty to animals against anyone, but I do not believe that there is any form of Epicurean "justice" involved in this, because Epicurus says that there is no such thing as absolute justice and the only kind that exists to even discuss is something that arises from agreement, and we have no such agreement with (most) animals.
As for that material on Hermarchus and vegetarianism, I also find that material difficult to trust and not nearly as clear as we would need in order to be confident of it.
So to repeat back the quote that I pasted above, I hear you talking about advantage in a way that sounds correct, but then you take that away with your conclusion that that "justice" is involved, because there was never any agreement with those rabbits in the first place.