In the Wikipedia article about Michael we have:
Unlike his two older brothers, Michael shuns the Corleone "family business"
In the first movie of The Godfather trilogy, the first talk of Michael Corleone is ambiguous in defining if he is against his family's business, because he talks about murder with much naturalness.
Apparently, he went to the army just to get away from his family world but also it isn't totally clear.
Is he against the family business or just indifferent?