Assuming you're only referring to people's individual, personal, lives.. There are friends of varying degrees of closeness, and there may be enemies of one kind of another. If someone has any personal integrity/character s/he will make good and certain that his/her behavior regarding either won't run the risk of being misinterpreted. There is a place for "war strategy" (even in if's not war, but is, say, competition between, say, corporations). But, in people's individual, personal, relationships there's no place for that (and it only amounts to a sneakier type of aggression).
If people don't know the difference between "war strategy" and what's healthy in a personal relationship then they need counseling because they've either been reading the wrong books or listening to the wrong people.
I think in our time where people live clusteres village or city times are changing with terrorism lurking in the shadows even if we try to believe we can see the best in people the question lingers "do I really know this person" yeah we can relate to family but can really glance and judge the character of people we meet everyday.