Executive summary:
1.) "I took advantage of an extraordinary event that turned out to be initiated by a rogue sell order, not legitimate trading."
2.) "Can I keep it? Look, here's why."
No, sorry. To allow the trade to stand would legitimize the attack, is that what you really want? (Besides bitcoins and dollars, I mean.)
+ 1,000
People are being too emotional. He was just lucky, he's done nothing wrong. If you want someone to blame, blame MtGox security and immature rule of the market. He's earned his pie fair and square.