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As human beings, we have needs, which we like to satisfy. Some of those needs can be satisfied through resources, or 'goods.'
If you couldn't grab those resources from your neighbor, how would you satisfy your needs? You can either make all your own things, or you trade with others. But to sell something you must first use your brain and your body to transform some things from something less valuable into something more valuable. And you can only sell those things that people actually desire.
Productive people are constantly trading. In order to satisfy their own needs they will trade essentially every day of their lives. They trade in other things besides goods and services as well. They trade information with others to better understand the world. They trade in companionship, in support, and in love. Every extra peaceful person also adds to our security.
Peaceful people are very beneficial. Peaceful people who have accrued large amounts of wealth have been, and generally are still, particularly beneficial to other people.
Contrast this with an unpeaceful person. Someone who steals, or rapes, or murders. These actions are harmful to people who are beneficial to us. Secondly, we ourselves or someone close to us could be the next victim.
An unpeaceful person shows through his actions that he doesn't know what society is about; he regards other people and their property as his own, and he tries to live at the expense of others. This has no place in society.
Morality is that set of principles of action that state that you cannot hurt other agents, or their property, who participate in society; for doing so must be detrimental to society.
What agents can participate in society?
Agents that can participate in society are so-called 'moral agents.' An agent is a being that can act. The second quality is that the agent should be able to understand the consequences of its actions. Finally, and most importantly, it should be capable to act in such a way as to not hurt other moral agents (other participants of society), or their property.
Aliens
If an intelligent species were to arrive on earth, they would most likely be peaceful. It is hard to imagine how an unpeaceful group of individuals would ever develop the technology required for such a journey. Secondly, technological advances make the spread of information easy so that good ideas beat bad ideas; and so peaceful and productive ideas would have long beaten unpeaceful and destructive ideas.
In that case there would be no reason to regard such individuals as anything less than human societal participants; and so inter-species societal integration is entirely possible.
Sleep and coma
If someone is asleep they are, for all intents and purposes, still a productive member of society. Hurting someone who is asleep (or taking their property) is just as detrimental to society as hurting someone who is awake. The same is true for someone who is in a coma, if it can be reasonably assumed that they will wake up.
Children
Children are beings who gain moral agency capacity as they grow and learn. As such, they should not be hurt. It is moral agency capacity that allows one to live in society. Children are also the next generation.
Proto-children
Proto-children are beings who haven't started their journey of gaining moral agency. At that point it is generally up to the mother to decide what the best future for her and her child is.
One element that gives insight into the development of a fetus are the establishment of thalamocortical [3] connections in the brain, which processes and relays sensory information and plays a major role in regulating awareness and activity. Before these connections are established, the fetus cannot be consciously aware of things in its environment. And so it doesn't qualify for the first part of moral agency (the agency part). One source states that sensory impulses cannot be reliably detected in the cortex at 29 weeks of gestation.[1]
From a societal view, you could say that after that age, and if someone is willing to raise the child, and there are no particular risks to the mother, that she should carry it through.
Separate societies
It is possible that a group of moral agents live separately from another group of moral agents. The best way to go about would be to have the insight and to stress the insight that both would be better off engaging in trade. This would also be the strongest way to avoid conflict, because if no trading occurs then the two groups will view each other as an opponents fighting for scarce resources.
[1] Essential Reproduction [4], by Martin H. Johnson and Barry J. Everitt, page 215
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