That would crash the price more than any actions fox could do. When you start doing anything like black listing coins or wallets you set a terrible option for future use.
You are right since it would only prove that bitcoin is not decentralized if community decides to do that.
So we thought that there is ultimate corrections that are happening during the latest dip but the truth is maybe MT Gox is probably one of the Big whales of Bitcoin.
Using maybe in your sentence might not be appropriate since it is a well known fact that Mt Gox held a lot of bitcoin when compared to other whales. I wonder though, how much btc from Mt Gox is left after the current dump?
For the stolen coin it seems impossible if the coin is back again, and that is very much in the fear of many people in this cryptocurrency world.
Stolen coins can come back in the circulation so long as the one who stole it remembers the private key of the btc address he used to store the stolen bitcoins.