As a player who sees toxicity and shrugs it off, I have to disagree about your extremely poor comparisons of League and real life situations. I'm not getting hit by a car when people call me bad. Nor am I hitting others with my car, or even my semi, if people actually think toxicity is that big of a deal, when I call others bad. Sure it might be an issue of self control, but really, the order is still: baddies -> lose self control -> toxicity ensues. I'm not saying it's justified; I'm just saying if you look at things that way, you'll understand the toxicity. Whether or not people will shrug it off like me is another issue.
I want to play with you so badly right now, Shjade. League boner right now. Duo queue ranked, yeah?
I never said I fail to understand it, at least in the circumstances you describe - as I've said, most of the time when I see people behaving that way they aren't even doing better than the people they're bitching at, they're just bitching because bitching is what they do. I said it shouldn't happen anyway. It's not acceptable behavior and shouldn't be excused by, "Well if you didn't play so badly he wouldn't have to blow up like that."
Most of the time when someone on my team starts blowing up at someone else, I'm in a position to point out something along the lines of the following: "Hey, <PersonBeingADick'sNameHere>. I know you think you're awesome and I'mma let you finish, but you have twice my deaths, half my kills and a third my CS. How's about you shut the fuck up about how you got 'stuck with this team.' Sound good?"
Or, more realistically given chat buffer restrictions and the need for typing quickly in game, "The scoreboard suggests you're worse than you think you are, slick."
I'm afraid I don't have any examples of someone carrying a team and
being toxic at the same time. The two states have proven mutually exclusive thus far in my experience with the game.
As for your proposition, even if I played ranked (which I don't, in large part to avoid the asshole behavior described above), I wouldn't want to play it with someone whose primary concern is winning. I don't need performance anxiety in my recreation, thanks, and I don't see the point in playing games with someone who isn't equally prioritizing fun in said games. It'll only lead to conflict.