the original result should stand at least. But as it was under the safety car, whether hamilton was in trouble or not, he was still moving so he shouldnt of been overtaken, that is in the rule book! look at vettel who tried it with three wheels, he couldnt of been overtaken under the safety car, yet there was clearly a problem!
The penalty is because mclaren didnt mention their radio broadcasts. However if stewards are to ammend a result like they did then they need to investigate everything, including radio calls. especialy as they are public now! So basically they have impossed a penalty on Mclaren for their own bad decision!