There are those who think that a hatred for evil is a natural extension of a love for good, and that to lack a visceral reaction to human malevolence betrays a lack of appreciation for what is good.
The truth is exactly opposite. Love for good and hatred for evil are wholly independent of and unrelated to each other. Indeed, those who pride themselves on hating murderers or terrorists more than other people usually do so out of fear that a true love of virtue would make them appear weak or effeminate.
In order to know that murder is wrong, one must first know why life is good. Life is not good because of the perceived glory that comes with fighting and punishing evil, it is good precisely because of the amoral pleasures and vulnerabilities that fearless defenders typically scorn.
The only justice is to act kindly towards those around you without regard for who they are and what they do or do not deserve. The virtue of my actions are determined only by themselves. Who I act upon is of no consequence. I will defend myself when necessary but I will always remember that there is no more virtue or value in self-defense than there is in any other biological process.
The man who howls for the blood of a murderer or terrorist "out of respect for the victims" is a nihilist and a thug. Negative morality does not exist, period. If the essence of good is opposition to evil, than there is no difference between good and evil. There are only different jersey colors, justified by nothing.
And this is why I will take care to be perfectly civil towards murderers, rapists, nihilists, and thugs.