You are the one who is supposed too ask him/herself why your lawful evil or neutral evil character is going on a murder spree. That is what role-playing is: making decisions in-character.
You don't want to do it, then don't do it and pick another path. You can even ignore the quest if you don't want to deal with it.
Doesn't that mean that for non-chaotic evil characters there is no path other than the good path right now? Larian seems to have specified the two paths as "good" and "evil" so surely there should be some room for nuance here.