You don't have the power to cause inflation. There is a material difference between stealing coins and double spending. Stealing coins implies you can rewrite a

You don't have the power to cause inflation. There is a material difference between stealing coins and double spending. Stealing coins implies you can rewrite anyone's balance to be your own balance. Double spending requires having counterparty, confirming a transaction with that counterparty, and then re-writing history to eliminate the transaction that the counterparty accepted. Coins that aren't in motion during the 51% attack can't be stolen, and coins that are in motion but aren't being sent from the attacker also can't be stolen.