keep in mind that this was not Dunkey's first offense and all we have at the moment is and automated system to dish out punishments. With the automated system it's much easier to filter out flaming and verbal abuse and by what Dunkey said in that one video, i'm surprised he wasn't banned for longer. If the only thing he said was that he wished that the malphite was gunned down in the street i think he would have gotten off with a chat restriction. The reason that they use an automated system is because there are too many games being played for riot's staff to police all of them. This is probably the only reason why the Malphite wasn't' punished, YET. There's mostly likely a case being built up against him and if he continues to intentionally feed he'll be caught, eventually.
I do agree that the system riot has now for punishing toxic behavior isn't very good, but it's what we have. However, Riot is working on an updated tribunal. and from what I've heard i'm exited about it.
It will include both pre and post game chat logs. the honors system will tie into this. So you can get "reported" for being a good team mate, nice, worthy opponent, or a toxic trash bag. When the case reaches the tribunal the playerbase gets to decide whether the report was valid and reward or punish the defendant properly. they want to include this because in the old tribunal people always went in with assumed guilt.
I'd also be nice to tie this in with a replay system with the chat overlay so you know what was said at what instance, but i don't have confirmation of this last bit.
until then this is the system we have.