Chat Restrictions

Ok I dont understand this. Ive been playing this game for 3 or 4 years now and have never had any type of game punishment other than que times from dodging or computer issues. I rarely have people tell me they are going to report me and im one of the very few people in this game that still has any type of honor ribbon. I was in a game earlier and was top defending tower vs 2 people........the other 4 on my team was bot and all died in a 4v3 fight. All the sudden the mid starts flaming me saying i wasnt with the team. Made no sense to me because i was 1v2 top and they had 1 man advantage in their fight. i tell him that and then the other 3 jump in the conversation. So yeah, i tell them to "stfu, you are intentionally trying to tilt me."

They all spent the next 5 min making comments harassing me so I muted 2 of them but then i see in chat another one of them all chat to other team to report me......then after game in post game chat all on my team were saying they were reporting me. Then i get into my next game and i get message saying i have chat restriction then after that game i get message saying i have it for 9 more games.

How is this justifiable in any way? Yeah i told them stfu but how does this auto lead to a 10 game chat restriction? I dont flame in games so i know there is no history of reports that lead to this.