Kenzi
Do you know what they did to her? Rebekah's tried to kill her more than once, is in fact the reason she became a vampire. Klaus killed her Aunt, used Elena for a blood ritual to make him more powerful. Kol was threatening to cut off her brothers arms when he attacked them, probably would have killed Elena if given the chance.
You believe in two sides to every story right?
Oh I've no plans to attack them. Its just nice for them to know there are people capable of it. Maybe it means they learn a bit of humility?