In addition to the encircling foreign marauders, Switzerland itself is composed of four different ethnic groups (German, French, Italian, Romansh) that get along as well as, e.g., Germans and French. They don’t even speak the same language.
Yet the Swiss peace prevails through the centuries. The Kaiser didn’t attack the Swiss. Hitler didn’t attack the Swiss (though he thought about it a lot). Stalin started to pursue some refugees into Liechtenstein at the end of WWII, but retreated rather than face the Swiss-Liechtenstein alliance. Terrorists don’t attack the Swiss.
Nobody attacks the Swiss. Not even the Swiss attack the Swiss; their crime rate is minuscule.
And this: Switzerland: nothing but cuckoo clocks?