Well, as is the case with just about every rule in the rulebook, it is inherently subjective. Its great to say that even if its late contact microseconds after the whistle is blown that a penalty SHOULD be called, but that's not really practical, because human beings don't have the ability to judge that in microseconds, which is why you see penalties that some people think are "late" non-called on a weekly basis.
In this case, I'm fine with the no-call, particularly when Sherman's contact is largely driven by the officials error in no blowing the play dead in time to avoid the contact. If I'm Sherman, I'm certainly no risking injury to myself to make a split second change in course in order to avoid contact that the officials didn't attempt to stop.
Again, there's the subjective "letter of the law" and then there's the practical enforcement of such rules in real time. Its why I always laugh off these post-game analysis of penalties enforced or not enforced, because they are utterly meaningless.
Which is why the rule states if there is any doubt or controversy, call the penalty. It's specifically written that way to cover "subjective" plays like this that happen in "real time". When in doubt, call the penalty. It's a note at the end of almost all rules in the NFL rule book. It doesn't matter when the officials blow the play dead - you can't hit the kicker, just like you can't hit a guy out of bounds - whether before, after or during the whistle - the whistle has zero bearing on the penalty. On top of that, Sherman is the one committing the initial foul - he knew he was offsides, whistle or not and proceeded to dive at the kicker. No one is suggesting he try to change his trajectory or "pull up" but that's still no excuse. Regardless of the reasons why, it still happened, and its a penalty. Period. The NFL confirmed it.
Isnt it funny, that the NFL confirms it was a missed call but then you have ppl argue otherwise lol. That is just foolish. There's no point in arguing with those types.