If I understood you correctly..
When ruling with pacifism you LOOSE gold when having military. I don't remember the exact costs but was it something like 1 gold/unit?
So if you just are into making gold, you don't want any army when switching to pacisfism. But that would leave you open for a attack.
Benefit from pacifism is 100% boost to GREAT PERSON points in every city where you have state religion. If you don't have religion, don't switch this on.