Like many people here I would suggest the answer to this is pretty straight forwards.
Smashing a rock would provoke a reaction in me of
"wicked, that rock was well smashed!".
Where as smashing a person would provoke the reaction
"good lord what have I done? I feel awful because of my ability to empathise with the person I've just smashed. Given that that person was alive and I took action to change that quality for no reason I can justify I feel extreme distress. As I would rather avoid said distress I will endeavour not to smash any one else in the future".
I would suggest that this is the long and short of it.
In fact these emotions are much more of a burden. if we don't have them it would be much better.
Only for individuals. As a society it is vital to maintain large populations that that are less vulnerable to extinction.
Edited by Larni, : 2nd point.
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