If all you said was "why are you coming when I am not there?" and "well, ty Lee -.-" I would not consider that to be toxic. Was it a little sarcastic/passive aggressive, sure. But toxic, no. To be honest, I would have to commend you on not saying more than that after he gave your laner double buffs twice.
It was a bit of a derp on the Lee's part, especially to do it twice, and it seems reasonable to expect him to know better by that rank. While "STFU IDIOT" is a bit of a flame, it's fairly mild compared to some of what I read in chat logs here, and I don't know that I would have reported him if that was all he said, but that's just my own personal standard and everyone gets to pick their own "report threshold."
There is something else that really should be said though. It's a bit of a misconception that people have, that Riot doesn't allow players to express discontent with their teammates or opponents. This is not the case at all. League of Legends is a competitive game, and people make mistakes that can, and do, result in games being lost. Riot understands this; their company is filled with gamers, people who are on the Rift playing in these same matches, and facing these same frustrations that we see. Which is why Riot has never said that players are not allowed to express their frustration or displeasure with the actions of other players. They merely say in which ways it cannot be expressed. And for the most part, those ways are ways that would be avoided out of common courtesy. Players are not allowed to express themselves in ways that are "unlawful, harmful, threatening, abusive, harassing, defamatory, vulgar, obscene, sexually explicit, or racially, ethically, or otherwise objectionable" to quote the Terms of Use.
In your specific situation, you are perfectly allowed to say something like "Lee, can you please not feed Orianna buffs again? It's getting hard to lane against her." You would not be allowed to say "Lee, you f%%%%%g dumbass. Get the f%%k out of my lane and don't come back. Report this Lee for feeding and being RaceOfChoice/SexualPreferenceOfChoice." You're allowed to say "Lee, I'm backing for Item X, can you do raptors or scuttle and gank after that when I'm back?" You're not allowed to say "Lee, you blind piece of s%%t, no wonder you can't you see I'm not in the lane. Who boosted you to Plat? Can they come be my jungler?"
A bit over the top, but you get the idea. I think a lot of people have become confused, or even a bit paranoid, because they don't understand the rules that makeup the Code of Conduct. Or because they think Riot is simply looking to punish every player for the tiniest infraction, and hoping to ban accounts as soon as possible so they can make players make new ones and buy all new skins. That simply isn't the case. There are millions of players across the world, and only a small fraction of those ever see punishment. It might seem a bit skewed if you read this Board, but this is also a minuscule portion of the player base and nowhere near representative. You don't have to be afraid to interact with your team, and even to express displeasure, as long as you are not a jerk about it.
