So, Yasuo players are known for being salty & toxic, but it's really not explained why, people just assume because they are weebs and play a high risk high reward champ, but that simply isn't true.
The true reason we Yasuo players get so angry is the way we get treated by other players, the problem isn't us, it's them. We most of the time get shit for even the smallest mistakes, while our champ is extremely difficult to play. You dont see Azir's get shit for failing an ult or fucking up their micro. Another reason is that we very rarely get help from our junglers, and everyone always just assumes we're toxic, and treats us like shit because of that.
Also when playing Yasuo, you will most likely be baby-sit by the enemy jungler, and even when you outskill the enemy laner, they will simply get ahead to the point where they dont have to do anything to kill you. And if you're playing top there's a huge chance the enemy mid will roam you too.
All this combined gets to the point where your personal skill doesnt matter, since no matter what you do, you can't do anything because you are playing your lane 1v2 or 1v3, and falling behind, becoming completely useless.
At that point it doesnt matter if you're a scrub or a pro, you will be garbage, and your team will not make it better. This kind of shit is extremely aggravating and puts people to the mentality that they are good and everyone else is thrash, because enemies are constantly getting ganks and you arent getting helped by your team. So frankly, I think it's totally justified to go on tilt from that, when your own personal skill doesnt make a damn difference.