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.
You are talking about nuance and all you can see is a dichotomy where Goblins = evil and Tielfings = good which means "goblins dead (kids included)/tieflings alive = good "and "goblins alive/tieflings dead = evil". You're characters don't have to give a rat ass about the Tielfings and their action can still lead at them being alive. Tielfings living are totally unrelated to how you role-play your character, it's a consequences of the decisions you made.
There isn't two paths, these are you options:
- side with the goblins + Haslin alive -> destroy grove + win DC with Minthara to have her you join you or fight her if you fail - side with the goblins + Haslin alive -> backstab them and side with Tieflings at gate (The path with the less deaths despite you betraying both groups once) - side with the goblins + Haslin dead -> backstab them and side with Tieflings at gate (next thing I'm trying, I'm hoping I can corrupt the Grove to the Shadow Druid still after it is done, but like all Shadow Druid stuff probably bugged) - side with Zevlor -> kill Khaga -> (no idea as I haven't done it) - side with Zevlor -> Expose Khaga -> (no idea as I haven't done it and it's partially bugged) - side with Khaga -> kill Tiefling (?currently bugged, you can't talk to Zevlor after Khaga asked you to deal with him) -> Ritual happen which piss off Minthara (if Haslin is alive he's sad he can't return to the grove when he shows up in your camp) - kill all 3 leaders because Haslin won't help you otherwise -> Tielfings live by association but you don't have to care - kill all 3 leaders because Wyll asked -> Tielfings live by association and you probably care (the path call the goody-two-shoes one despite it having you kill more than if you raided the Grove) - Haslin dead (regardless of how, he can die as a temporary companion while clearly the temple) -> once you read his journal you can just ignore the side quest of dealing with the refugees and continue on with the main quest
Explain to me why you think only the first option fit an evil character?