You’ve got different sticks. If someone gives your anecdote to an experienced LoL player, they’ll immediately go to the all-too-common person intentionally ruining the game of another by playing poorly, not listening to advise and being abusive in return (or just plain going AFK).
The sort of situation you’re talking about normally comes from us as “X was suffering in the game and thought he might quit because he hated it so much.” That only ever leads to support from us. I can’t count how many players we’ve brought through the ranks and continue to play with of all sorts of varied abilities.
It’s simple culture clash (of sorts), that’s all. McKnight has never told a player he outright is bad (except the actually bad ones like me and Chris and hey McKnight! You suck). McKnight’s also one of the few players that takes the game semi-seriously in the EU Mumble so there’s that sort of culture-clash too.
Calistas, I’ll break down for you why Corki’s a better champion than Tristana in a rough and ready fashion.
Overall, Tristana is built as a hard carry. She’s very item-reliant and has a long ramp-up time. This is not helped by her not being the most efficient farmer (no good AoE- her E doesn’t count!). Corki’s got a much faster ramp-up time and due to the burst potential of his abilities as well as the AoE nature of them, a much better ability to farm and a higher total damage potential. He’s a less hard carry.
Stat-wise they’re not much different. Corki gets a slightly better damage build and they’re almost parity on health. Corki has more mana but needs a lot more. They both have the same base movespeed (300 is standard for ranged characters. Melee are faster).
Ability-wise I’ll do a quick ability-by-ability breakdown:
Tristana’s Q is a pure steroid skill. It’s the main reason she scales so well into the late game, and it’s one of the better pure steroid skills in the game (there are some better hybrids like the frankly broken Impure Shots). However it isn’t much more than a steroid skill because it doesn’t need to be. It scales perfectly with AD. Corki’s Q, on the other hand, has some soft-CC utility and is an AoE attack. It softens up creep waves allowing him to farm well and the CC part of it can save his life in the way Dodge can. Tristana’s Q is better late-game, once she has items, but Corki’s Q has more early-mid utility.
You mentioned his CC not breaking channels like Trist’s R. Well, to be honest, Tristana shouldn’t be in the position where she has to break a channel. That’s the job of the supports and tanks (and Exhaust-carriers, if necessary). She should be concentrating on killing people. Stopping people killing her is the job of her team.
Both have escape moves on their Ws. Tristana’s has the on-kill reset and a CC component (more damage), Corki’s is faster, I think (point-to-point) and does more AoE damage (I think). About parity (I think).
Corki’s E is where he proves that he’s a better champion. It’s an AoE armour strip that also does a portion of his attack damage. A carry with an armour strip is ridiculous. Very few characters have resistance strips, and an armour strip on an AD carry adds that much more to his damage potential. It’s also a brilliant, brilliant farming tool. Tristana’s E is almost pointless. Yeah, it’s semi-useful for farming and it’s an anti-heal but it’s underwhelming on a ranged carry.
Ultimates are where Corki dominates. Rocket barrage gives him some massive, massive AD-based AoE burst damage. Load up a Big One with pokes, wait for a team fight and unload the whole lot. You don’t even have to aim to get a few kills. It’s a much more useful ability than Buster Shot, which is admittedly a good piece of CC.
Passives? Corki wins. His passive is, I contest, a stupid one. On-hit true damage on a carry? Seriously? Tristana’s is nice but not as good carry-wise.
The main reason, I hope you’ve picked up, that Corki is a better character is because he can farm that much better leading to heavier items and does AoE damage with good utility/on-hit effects. He’s just harder to play because his ability range is quite short and he’s a bit glass cannon. Tristana’s a classic Hon/DotA style massive-damage-to-a-single-character type carry.