First off, we're 1 for 4 since the "Little Brother" comment and it will never die because the media won't let it. Roiling up the in-state fanbases is good for radio talk-show ratings, comment page hits on newspaper websites, etc.
Second, Dantonio won't let it die because that is the tool he's used for the past 5 years to rally the players and fanbase behind him. He's taken one comment from one player and exaggerated it to become the default stereotype of our fanbase and program. Dantonio needs to push the idea that Michigan has no respect for MSU because it gives him tacit permission for all of his shenanigans.
The ironic part is that as much as Dantonio pushes the notion that Michigan is disrespectful of MSU, aside from Mike Hart, I can't name a single instance where a U of M representative publicly disrespected State. Yet in the 5 years since the 2007 game, Dantonio has disrespected U of M every chance he gets with snide remarks about, "Where's the Threat" and "60 minutes of unncessary roughness". He treats Michigan assistants rudely in public seminars and engages in all sorts of asshattery and the MSU faithful put up with it because he's engrained in the collective subconscious of Spartan Nation that somehow, Michigan has this coming to them.
It's going to be fun to watch how the tolerance level for his antics start to drop once the wins against Michigan become scarce again.