Simply deleting the wallet would not be enough.  Most of us figured out pretty quick how to copy or replace the wallet.dat someplace safe.  They can delete my whole hard drive, burn down my house, and lock me up for 20 years and I'm pretty sure I can at least get my wallet back. To really do any damage, the coins have to disappear.  To do that they'd have to get the wallet, decrypt my password, and send the coins to never, never land. Easy enough for a couple of thousand wallets, but to hurt the whole community, doing it millions of times before we caught on would be daunting even for a quantum computer.