Other than the fact he had no knowledge about her plans to steal anything, as he personally states multiple times in the quests after the attack? How about Genn yelling to Sylvanas to come out to face her executioner on his ship?
They are citizens of Undercity. Forsaken are their people in this context.
Yeah, it's not like each faction of WoW, Alliance races included, don't take lightly to traitors and defectors.
You mean the oath you twisted? They are free to go their way if they don't want to serve Sylvanas.
Why would a Goblin be more concerned about something that isn't profit? Also, the Alliance spies snooping around in a Horde camp, whatever snooping referred to, is a hostile act. And regardless of the wording used, the Horde quest giver does refer to the spy activity that has been detected. Meanwhile the Alliance quest giver, despite mentioning the first group of spies, says nothing that would indicate them already having been killed or even attacked.