RIOT give me a reason why I had to take this loss

http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/2143089351/37822565?tab=overview One of us left at 6th minute without saying anything, our team tried hard but u just cant win 4v5. Now 4 of us have to take the same LP loss with this rek. Give me a reason, what u cant detect it? YOu ban people to talk shit but you dont ban this kind of people?