Well it all depends on what a fictional person's (real-world) religious beliefs were and I don't want to go any further into that because it would likely needlessly offend real life religious members. My point in bringing up the impact of Michael's actions on his "soul" or psyche if you will is that they disturbed him, were not good for him or his personal family and were not things that set well with him or other people. In GF1 arguably Michael is acting in self-defense and defense of his father and brothers. In GF2 he is an aggressive power-mad expansionist. He's become exactly the sort of big-shot that his father started out resisting. His actions are much less defensible. As we know, FFC wrote it this way very much on purpose.

If IRL Maglicco could get a pass from people he wasn't related to despite having temporary control of an separate power structure (The Profaci Crime family) then fictionally Michael could have given a pass to his pathetic brother , who had no independent power structure and was very much under Michael's thumb. Did he deserve such a pass? If you think that he was directly and knowingly involved in trying to kill Michael and Kay, then obviously not. I think the film is deliberately ambiguous on that point thus the discussions over the years.