There is a lot of confusion that arises when a non-universalist talks to a universalist. Let me give you an example so you get an idea of what exactly I mean when I say universalist/non-universalist. Imagine a man who travels to a strange land. He inevitably gets hungry and goes to a street merchant who is displaying, what look to him to be strange insects and some fruit. The visitor says to the vendor, “May I purchase some food”, so the vendor gives the guy some bugs, to which the visitor exclaims, “that’s not food”. The native had a more universalist definition of food, than the traveler. Now another example. Many Indian tribes in North America had a name for themselves, this name roughly translated, was “human”. So when a white man would discuss “humans”, the Indian had in his mind his tribe, while the white man had in his mind the entire population of the earth. Now this difference of outlooks can be reconciled with proper definitions, and an agreement on the definitions of words and terms, but without doing this, the universalist and the non-universalist will in actuality be speaking different languages.
Some religions are universalist and some are not. My main concern currently are the differences between Christianity and Islam from a universalist/non-universalist perspective. Christianity is a universalist religion, when Christians read, “Thou shall not steal” (Exodus 20:15) they apply that universally; they believe they shouldn’t steal anything from anybody at any time. Non-universalist religions (Islam and Judaism for example) are more nuanced. Here is the Koran “As to the thief, Male or female, cut off his or her hands: … (Koran 5:38). It seems that Muslims should not steal, but the Koran also says “So enjoy what you took as booty; the spoils are lawful and good” (Koran 8:69). It also appears that Muslims can take things without any punishment at all. So why the two seemingly contradictory verses? How these two verses are reconciled is through non-universalism, stealing from a Muslim is wrong, stealing (and killing by the way) from a non-Muslim is okay.
It has to be said that, like many things, doctrines exist on a spectrum, there probably doesn’t exist any true universalist doctrine, or any true non-universalist doctrine, but that doesn’t negate the fact that when two doctrines that exist on different ends of the spectrum come into contact there are problems.
As for taking from unbelievers, perhaps the most illuminating example among many comes from the aftermath of the battle against the Khaybar, as recorded by Muhammad’s earliest biographer. The Khaybar were a peaceful community of Jewish farmers who did not even know they were at war until Muhammad led his men against their town one morning, taking them by surprise and handily defeating them.
Not only did Muhammad take much of the town’s possessions and land, but he actually had the tribe’s treasurer, a man named Kinana, tortured until he gave up the location of hidden treasure. Muhammad then beheaded the man and “married” his traumatized widow, Safiyya (who passed through the hands of one of his lieutenant’s first, due to the luck of the draw). (Ibn Ishaq (764) )
If it be possible, as much as lieth in you, live peaceably with all men. (Romans 12:18)