While I can agree with how you look at it, Riot does not take that stance. They like to do the I dont care who started it, im finishing it approach. They also like to tell players it's not their job to defend themselves (Which is BS considering I was banned for not defending myself and agreeing with players insults)
What makes this sad is that Riot does not like to do much for the people provacating reactions from other people and end up targetting the people who say something back. If someone has a history of trying to get negative reactions out of people and are NOT directing comments towards themselves, then they need to at least get a notice making them aware that their actions are not helpful.
The issue isn't that Riots doing their job incorrectly, they just have a messed up behavior system. If you're being called a feeder/you suck/uninstall and you respond to this, Riot sees you being as bad as they are. Even if you didn't flip out at them as long as you respond to them, you're instantly in the same boat as they are. If they decide to report you for responding to their comments, this immediately makes you the bigger target because Riot puts so much emphasis in "It's not your job to defend yourself" that to even say 'no i'm not' makes you breaking what was just said.
That's just a bit from the riot side, the other half of that coin is the current tribunal. The way it was explained to me was that the only people who have any say as to what is considered 'acceptable behavior' are the people putting in the reports. So those people that we hear about in the boards but get downvoted because it doesn't matter how other people behave as long as you're 'just as guilty', those are the people setting the standards. They are the ones saying what is acceptable and what isn't. The players that play this game without trying to be 'toxic' and just play for fun (I used to be this player) dont get any say in the matter because we don't report anywhere near the same amount as the people who take offense over everything do. So my view as what should be acceptable because I dont report people will differ from the people who report people after almost every game.
Some of what I've said is mostly my view on the matter but the reasoning behind my views on this is enforced by what Riots Behavioral specialists have told me when not dealing with my 3 months issue.