Are you referring to recent history?
We all know that nazis killed many clergy of all types in WWII... including many, many nuns and RC priests as well as those of the Eastern Orthodox Church.
Wonder why in Croatia there were any, so-called, RC clergy involved with nazis??? Surely, the Croatians knew that the nazis were the enemy of ALL REAL CHRISTIANS.
I think the nazis were able to find weak links in almost every group by appealing to that groups highest level of hate toward those they found different than themselves.
In the Yugoslavian case, this appears to be just what the nazis were able to achieve. Use racial and religious troubles or differences to get co-operation from certain Croatians.
In the end, the nazis LOST and all Yugoslavia became commie. Another group of Christian haters took over.
Lose, lose situation for all Christians, EOC and RCC. And, for the Jews and Gypsies as well.
What a shame.