Violent, territorial and defensive behaviour has evolved in most animals due to limited resources and a willingness to survive and procreate. Resources will always be limited since populations will grow until they exhaust the supply. Animals living peacefully next to each other will always be in slightly different ecological niches (prefer different kinds of grass, fruits, etc.). Social and compassionate behaviour are just a "further" development of evolution and the beneficial attributes of living in safe organised groups.
You can be an optimist and hope that humankind at one point will learn to get along with each other or re-write the evolutionary basis of your species.
Since as stipulated social behaviour stems from deeper evolutionary behaviour you would need to take away the reason for a species to fight over resources. This would mean that your species would need to be able to survive on a resource that if you consume it doesn't hamper the other individual, or at least he can't do anything about it. The first thing that would come to mind is whales (the plankton eating kind), they eat plankton and so can't really defend or deny other species that resource. Procreation can lead to fights, (don't know for whales) but by procreation by shooting sperm into the water in the hope a female species getting pregnant should alleviate this problem. Having no natural predators would help in having no defensive behaviour instinct.
I think other resources with this kind of characteristic can work as well but I can't think of any.
EDIT: Your vampires bats are actually a nice example, their "peace loving" behaviour stem from the fact that they need to eat every night otherwise they die but the changes that the are always successful in hunting is only 2/3 (can't find the link to the New Scientist article about this). The other 1/3 of the nights they need to get the food from successful hunters thus creating a need to be sociable. This might indeed be a nice way of forcing social behaviour that you can use, I only wander what happens when groups of bats collide.