Kalista's Black Spear

I was playing with a teammate who decided to pick Kalista. Without any type of communication or my consent, she decided to use her black spear on me (in the middle of a team fight!...I am the top laner, not her support!). I assume the other player did this for the laughs but I decided to follow up his joke by leaving the game, for which I receive a penalty... Please either change the dark spear mechanic or allow people to deny the binding...