The infliction of cruelty with a good conscience is a delight to moralists. That is why they invented Hell.
Science does not aim at establishing immutable truths and eternal dogmas; its aim is to approach the truth by successive approximations, without claiming that at any stage final and complete accuracy has been achieved.
Suffering to the criminal can never be justified by the notion of vindictive punishment. If education combined with kindness is equally effective, it is to be preferred; still more is it to be preferred if it is more effective.
There is no need to worry about mere size. We do not necessarily respect a fat man more than a thin man. Sir Isaac Newton was very much smaller than a hippopotamus, but we do not on that account value him less.