Maybe they do. How can you say with 100% certainty that they do not?
All I have done is tossed out the name of someone I would like as the Lions coach. Why D you feel it necessary to attack that when you are not that person, have no idea what he would or would not do, what motivates him and what doesn't...yet it is important to you to say it is absolutely impossible and mock any potential reason he might have on a personal level as being stupid. You do not know him, who are you to say what he will or will not do?
If you wish to argue against him being coach because he wouldn't be a good fit or whatever, fine. But there is no more reason to assume he is desiring to coach at USC than coach for New Orleans, Kansas City, Miami, Detroit, or any other potential job opening.
All I have said is with Jim coaching at UM, there MIGHT be a family bond that would appeal to him going to Detroit as opposed to elsewhere. You are behaving like I said something extremely outrageous. It has a percentage, albeit small, chance of influencing him to come to Detroit. Of course it might also be a reason for him to never consider Detroit due to some family issue, but I have never seen anything in their relationship to suggest they would never be able to live that close by. This isn't about you or anyone else's familial relationships, only there's. So give me one, just one specific example of how they despise each other enough that it would prevent John Harbaugh from coaching the Lions.