I realize it's a rule and I realize the MSU player did run into him, so technically speaking, yes - it's a penalty.
On the other hand, it's the freaking first ever Big Ten championship game...you want it to be determined because a legitimate player (i.e. non-punter) went hard after the punt and happened to run into the punter? And plus, did you happen to get a load of the super slo mo replay? The Wisky punter could have easily kept his feet - watch the replay, he clearly lifted his foot up so he could "make it look good".
I'm sorry...by the letter of the rulebook, correct call. But as far as being a legit game outcome - total bs. Load of crap.