Monsterous races are fine to me and most players, but WOTC have stated that none of their races are meant to be inherently evil anymore. If they want to push such agendas, then they should enforce them as well and at the least remove the ability to be able to kill the two Goblin children.
You still don't differentiate between "race" and "society/culture"... goblin society is undeniably evil (they delight in torture and cruelty, bullying those weaker than themselves, etc). A goblin that is brought up in a different culture wouldn't necessarily have those tendencies, therefore the "race" goblin isn't inherently evil. That's basically what WotC meant.
Originally Posted by DumbleDorf
Who decides what the moral and ethical scope is meant to be in a D&D setting?
The DM does. If players have an issue with a DM's decision, they are free to find another group to play with.
Originally Posted by DumbleDorf
'Tieflings are invaders from hell that need to be destroyed like the devilkin they are and sent back to hell' - what is wrong with roleplaying such a perspective? Do the Githyanki spare children when deciding to slit people navel to throat as Lae'zel so exquisitely details?
There's nothing wrong with roleplaying a character with that perspective, you just need the right group to play a character like that.