Ok, lets have a civil discussion in regards to the behavioral system. Always open to this, especially the ones that have good ideas that can be expanded or tweaked. I'll split this up in 3 post so I can TLDR it.
3/3 - TLDR: Riot needs more visibility on the system
The truth is, the system is very open-ended, it's only making banned players come back on other accounts and it somehow manages to miss the big stuff while going after every little thing. The whole system fails when banned players are able to make as many accounts as they want for free and when players stop supporting the game due to the system.
When Riot permabans someone, their philosophy is "the chances of this guy reforming isn't a whole lot, we'd rather not have him in the game". Thus in their eyes, they have already written off the toxic player as a paying client.
From a business standpoint, do they want to remove the toxic guy who has spent $500 but is causing a negative environment for 4-9 other players in every game? Those non-toxics are also spending $500 and probably will spend more, promote the game more when they are enjoying the game AND they won't cause a negative environment.
I personally think it is a fine argument to protect the ones that are paying money and aren't toxic rather than protecting the ones that may pay the same amount but are toxic.
Now towards the point of how they miss the mark on the big stuff. I'm guessing you'd be referring to the hate speech toxics, the 'kill yourself' toxics, the intentional feeders, the AFK as a method of griefing.
This is also a common arguement the toxics make, "I said this mild BS and I get banned and yet they say so much worse and nothing happens to them??". This also causes people to downvote them as people are responsible for their own behavior and punished in their own time depending on how frequent they are toxic. Other people will get their punishment in their own time when they hit their punishment threshhold.
So how can this be improved? This is actually a problem that Riot has already acknowledged this problem, it is "poor visibility of the behavioral system". Due to how the notifications work, where you only see the notification if your game you reported got someone punished, and not if they got punished down the road. This has made many people feel that the system doesn't do anything because they don't see the system working.
A Report Card system or something similar would be a nice to have. Tantram mentions that he built something similar for ThunderDome. While we won't be getting exactly this, we may be able to expect some form of "report card" to improve visibility of the system.