"a person unrepentently engaged in grievous sin should not be given a highly trustworthy position"
I honestly don't mean this sarcastically. Doesn't the above describe just about everybody?
I mean that in all seriousness. Hate, pride, adultery, sex before marriage, overdrinking, overeating, birth control, lying, self-rightousness, and anger, just to name a few, are all sins, grievous ones.
How many of us could be in a high trustworthy post?
Remember Clinton? One of the reasons conservatives loathed him was his disgusting immorality. Gross immorality in ones' private life seeps into the rest of one's life. Doesn't mean everyone who is flatly immoral is unfit for everything. There are degrees of immorality, and some positions are more sensitive or carry more weight than others.
Not all moral failings or character flaws are equal. The understanding that serious moral turpitude renders someone unfit for public service or a position that requres security clearances or other types of heavy responsibilities used to be common cultural understanding.
I am not passing particular judgement one way or the other regarding Santorum and his aide. We are not privy to the particulars. I have other reasons I do not love Santorum, although I like some things about him.