As was pointed out by ESPN when Rondo got the suspension, Rondo has a past history of offenses. Suspensions are typically only handed out for 1) really bad offenses (Bynum) or 2) a repeat of a relatively minor offense. In this case, Rondo is the latter.
League officials even said at the time that it wasn't because what Rondo did was that big of a deal, but because of league rules about multiple offenses. That wasn't the first time Rondo had done that. This is the first time Noah had done it. Simple.
So take off the tin-foil hats, eh?