I watched the Mears/Pendleton moment in slow mo. It looked to me very like VP came across the sprint line and then KM elbowed her as a consequence of that, not the other way around. Which makes the decision fair and proper.
A shame, but rules is rules.
3.2.042 During the final sprint, even if launched before the last 200 metres, each rider shall remain in his lane up to the finish, unless he has at least a clear cycle-length lead and shall not make any manoeuvre to prevent the opponent from passing.
(text modified on 1.01.02).
3.2.043 A rider may not challenge or pass on the left an opponent riding in the sprinters’ lane.
If the leading rider leaves the sprinters’ lane and his opponent attempts to pass to his left, he may
not return to that lane unless he still has a clear cycle-length lead.
3.2.044 A rider passing on the right of his opponent, who is in the sprinters’ lane, may not crowd him or cause him suddenly to reduce speed.
So the rules are open to interpretation by a commissar that wants to show who's boss. Mears leans on VP first and has to shift her ass sideways to do so, VP drifts slightly outside the red line on the straight but this has no effect on each rider as they approach the line. On any other day no action would be taken, they both finished thinking that was that and onto round 2.
A great contest ruined by a commissar who has a funny way of interpreting the rules.