Toxicity should not be a bannable/punishable offense in any circumstances, there is literally a mute button, if someone is being toxic (verbally) then just mute them and get on with the game.
I'm gonna get to the first part of this sentence later, but for now, let's just address the argument of "there's a mute button";
There's literally a set of rules you agreed to, if you're being toxic, then you're going to get punished for breaking those rules.
The existence of a mute feature does not overwrite the rules you signed up for; and, wouldn't you know it, the use of both the mute feature and the report feature are not mutually exclusive. Riot gives us a few tools to deal with toxicity, it's only right that we use them all liberally.
There is a REASON for the mute button for chat/emotes/pings, and it's definitely to ignore BMing and toxicity.
But it's not to allow toxicity. The reason for the mute feature is to prevent further frustration caused by emotes/pings/chat; whether someone is using them maliciously or otherwise.
And, I say again; it does not prevent the rules from still being in place, so toxicity, even if muted, is still punishable.
If you're being toxic to a person who was being toxic first, they should be investigated as well if they're the ones who make the report considering you're basically defending yourself/others from that toxic person.
So...I don't get this one, you're lobbying for toxicity to be allowed, but then you want to get punished for your own toxicity if you decide to get into an argument, or...What?
Here's the deal; if Player A reports Player B, the IFS will only review the behavior of Player B, as they are the only ones whose behavior has been highlighted for review. Player A did not report themselves, so their behavior won't be reviewed unless someone else reports them.
If you want to see someone else punished for their toxicity, report them yourself, don't expect Riot to make some backwards system that punishes the person who files the report instead of the person being reported - assuming any degree of misbehavior from both parties, of course.
Also, you can defend yourself without being an asshole back. There's literally a mute button, after all. Just mute them and get on with the game.
I understand the concept of sportsmanlike conduct and stuff but that should only be in physical sports where things CAN escalate, where things CAN get physical, where you CAN'T just press a mute button.
So you're saying things can't escalate in League just like in physical sports? You're telling me, that there's no way, not a snowball's chance in fresh monster hell, that someone could get pissed off from someone being toxic to them, and then decide to troll or intentionally feed?
Sportsmanlike conduct has a place in all sports, be they E-Sports or physical sports. And whether you think so or not, shit can escalate in League just as it can in physical sports, the only difference is in how.
If someone is running it down mid, that should be bannable because you can lose for it.
I'm sorely tempted to call a double-standard here. Although, I'm of the attitude that all toxicity has no place in League, so I'm just going to point out something else;
Flaming your team and being toxic is almost as bad a case of sabotage as trolling or intentionally feeding. You waste your time on typing, you bring down everyone's morale, making everyone play worse, and you also make people not want to cooperate with you, ruining team cohesion and decreasing your odds of winning.
You can deny all you want, but your words do have impact on others, and how you choose to use or abuse that impact can greatly affect the outcome of the game. There's a reason that we have a Loading Screen Tip that talks about how toxic players lose 60~% of their games.
You shouldn't be banned just because some toxic person is calling you names, grow up, Riot.
Or, how's about toxic players grow up and not call people names in the first place? That behavior is pretty childish, and I find it ironic that you're telling Riot to grow up when they're simply punishing them for acting out.
Words can't fucking hurt you...
Words can hurt some people. You can't speak for the sensibilities of all human beings, much less for the League Community as a whole.
...especially if you have a mute button.
You can reiterate the existence of the mute button ad nauseum, but it still will not change the fact that the rules exist too.
And the Code of Conduct & Summoner's Code which you agreed to follow > the mute button every single time.
And if you don't like it; them's the 8r8ks.
...and if you think words CAN hurt you, you probably shouldn't be playing something as toxic as League of Legends.
Thankfully, there's a world of difference between thinking and knowing. And I don't think words can hurt people; I know.
And those who can be hurt by words have every right to play League too. You don't get to play arbitrary gatekeeper for a game you don't own.
Now, back to that first statement;
Toxicity should not be a bannable/punishable offense in any circumstances...
If you want toxicity to not be punishable, you have to prove that there is enough benefit to toxicity to outweigh the negatives; which is, to say, what I outlined earlier;
Flaming your team and being toxic is almost as bad a case of sabotage as trolling or intentionally feeding. You waste your time on typing, you bring down everyone's morale, making everyone play worse, and you also make people not want to cooperate with you, ruining team cohesion and decreasing your odds of winning.
If you can prove that there's any benefit to toxicity that greatly outweighs these drawbacks, then you might have a case for why toxicity shouldn't be punishable, but until then, these drawbacks give us every reason to see toxicity punished.