This is your 4th penalty within 4 months. You were not banned for a high volume of reports, you were banned because of your behavior. Reports flag games for review.
The first 3 times you were punished, you were told your behavior was not acceptable. You were given 13 games of your chat logs for these first 3 penalties, illustrating the types of behavior that are not tolerated.
You chose to ignore the warning that the next penalty of any severity would result in a permanent ban of your account.
You have a tendency to chat about things that aren't happening in an attempt to 'frame' other players who you want penalized. You threaten people with getting them punished pretty consistently.
I couldn't report him. I wasn't even in the post game lobby for 30 seconds before I was disconnected and received the ban message.
It was more like 5 minutes after the game in your case. You had plenty of time to report a player. You chose to use the time arguing in post-game chat.