The fuel sampling reulation from the 2012 Technical regulations
6.6.2 Competitors must ensure that a one litre sample of fuel may be taken from the car at any time during the Event.
Except in cases of force majeure (accepted as such by the stewards of the meeting), if a sample of fuel is required after a practice session the car concerned must have first been driven back to the pits under its own power.
So if a car has to get back to the pits under it's own power to provide a fuel sample in practice and qualifing. The same should hold true of the race itself.
I don't think anyone has said McLaren shouldn't have been punished. But perhaps a fairer punishment would have been to exclude the Q3 times.