Rebuttals from Smart People

Specifically, CS Lewis rebuts... Michael Ignatieff:

The most dangerous thing you can do is to take any one impulse of your own nature and set it up as the thing you ought to follow at all costs. There's not one of them which won't make us into devils if we set it up as an absolute guide. You might think love of humanity in general was safe, but it isn't. If you leave out justice you'll find yourself breaking agreements and faking evidence in trials "for the sake of humanity" and become in the end a cruel and treacherous man.

And while we're at it, CS Lewis rebuts Paul Martin:

Of course God knew what would happen if they used their freedom the wrong way: apparently He thought it worth the risk.

Both from Mere Christianity.