Rhonin broke his neutrality first which makes Rhonin a casualty of war not a murder victim. If stand inside a battlefield and get killed what do you expect?
One mage betrayed dalaran and you know what he helped Garrosh escape his trial so he betrayed even horde. Also Dalaran helped alliance move divine belö through dalaran to teldrassil and making magical defences there which put alot belfs on hardplace as Dalaran was speaking of neutrality but their leader helpes to murder their families.
Both instances were fault of dalarans own leadership and they forced hordes hand.