How religion can be both a unifying and a dividing force?

When two people believe in the same religion it unifis them because they not have someone who shares their personal views and moral standards however, say a man of another religion with the same views and standards but of a different religion comes in, an intolerant person would immediately exile said person, so in this way religion is dividing because people that, most likely, would be friends and get along greatly are now separated by theit varying concept of "religion".