Seems like a good natured troll but I'll bite

the argument of, it's different because their culture/race deserves it, isn't a good foundation for hatred of the evil path.
Eh. Keep on the borderlands was one of my first DnD experiences. They're goblins, they're evil, killing them is
good. But if you don't accept that they are inherently evil you can judge by their actions - which are evil. Evil is a physical force in Faerun - that's why protection from evil and dispel evil works.
The three kids killed someone and are bragging that this is their first kill. Imagine finding this in your neighborhood -- would
youth excuse such actions? Even if you are nice to 'eight' he says he wasn't all that upset about the death of his parents. If you take Lae's advice and beat them a bit they will surrender and, yes, killing them at that point is an evil act.
While I don't think EA Wyll was right to kill the windmill goblin after he surrendered I think his statement after that is right. If you let this goblin go he's going to kill more innocents and the blood of those the goblins kill is on your hands.
Yes Halsin always takes a swipe at one of the two goblin kids who are showing themselves to be evil.
So while there are exceptions to the rule - like the goblins in IWD and SoD - the rule still stands. These goblins killed Miri and bunch other people gathering for a wedding. Even if they were freed of the Absolute they would be doing the same thing in the name Maglubiet.
So I clean out the goblin camp and blighted village and I feel like a hero when I'm doing it. Even if I didn't save any of the kids from the grove I probably saved another wedding party.