Wikipedia:You can't squeeze blood from a turnip

You can't squeeze blood from a turnip. – Anonymous

You can't get something out of someone who simply doesn't have it to give.

If a standard remedy exists for an editor who has done something wrong and the editor shows no sign of regretting the mistake, then go ahead and apply the standard remedy.

Extreme gestures of good faith need not be extended toward an experienced editor who consistently violates fundamental policies and rebuffs appropriate overtures. Some troublesome users do not want to change and the community's energies are limited.

Indeed, you really can't squeeze blood from a turnip.