To be fair, they had no pressing reason to refute....
....its fraudulent nature.
If they would have refunded the sum on accepting that it was fraudulent, then they might have been less willing to accept it. As they are unwilling to refund the sum in any case, why dispute the nature of the transaction?
Sony: "You need to pay us £50."
Punter: "But I didn't complete, or authorise the transaction"
Sony: "We're sure you didn't. We will, nonetheless, be needing that fifty quid."
As bad as the PR on this is, it'd be much worse if it went like this:
S: "You need to pay us £50."
P: "But I didn't complete, or authorise the transaction"
S: "Our records show you did."
S: "Oh you're right - you didn't! We will, nonetheless, be needng that fifty quid."