Yeah and you try telling that to someone you just sacked who has no respect for you or the company any more. They don't give a damn it isn't personal, once their obligation to behave like an employee goes they'll hate your guts and now they've got nowhere to be tomorrow? Ahh, who cares if they break their hand.
Best thing to do when someones purpose lives out it's usage is fit them in somewhere else, treating your human capital as expendable is a surefire way to get the bare minimum from your employees. If you save someone from redundancy or help develop them to make of for their shortcomings they'll be in your pocket for a few years at least.
Sacking should be a last resort like I say, the worst companies I ever worked or consulted for were the ones who didn't care about staff - they just hired a load of clowns through an agency and sacked them off at the drop of a hat.
You sound like a HR rep by the way, how does it feel to have a fake job while the rest of us do something productive?