One is not like the other, each is unique. Similarities exist, drawing some together, but there are always differences… it would be boring without them.
When one group has differences that conflict with the differences of another group, there is always a problem. To what scale that problem rises depends on one or the other group insisting that the other change and adopt their differences.
As long as they are separate, the differences are irrelevant. When circumstances arise causing one group to influx into the area of another, that is when violent conflict may arise. When the invading group will not change to accommodate the differences in their host group’s area, turmoil is guaranteed. Time may cure this unless the ideology of the invading group is resolute and renewing. If the structure of the ideology of the invading group is rigid there are two ways it will resolve. Either the host will change, or the host will destroy the invader.
Differences between groups will always insure that conflict will be present whenever the groups meet.
This is how mankind stands today.