Don't say "pick a champion", say "build a unit".
"Whenever I face zerg, they always go mutas and I lose. And don't say build stalkers to counter, I shouldn't have to build stalkers to win the game. What if I want to go carriers?"
"Guys, I don't understand why my team gets angry at me when I announce my intention to rush battlecruisers no matter what. Battlecruisers are fun! Isn't this game for fun?"
"Stalkers are too good. They are strong against everything and have no weaknesses. I refuse to use them because I have honour, but I keep losing to them and now I'm in bronze and I don't deserve it!"
"There is NO counterplay to ultralisks! Unless you have range, but ultras are just a big fuck you to all melee units!"
"BG NOOB VOID RAY SPAMMING NO SKILL NOOB YOU ONLY WON BECAUSE I HAD NO ANTI AIR"
"Dark templars are anti fun, if you don't have detection there is nothing you can do and it sucks to spend money on detection to win the game!"
"The meta is for sheep, I'm going to build factory before rax and rush them with 20 widow mines! Whoops, I lost because I didn't have a rax and they just walked in. Blizzard enforces the meta!!!!!!"
"This game sucks because Blizzard only cares about KOREANBIG$PORTS. Proxy cannons are unstoppable in bronze, but Blizzard doesn't care about bronze!"
Silly, isn't it? People keep forgetting that this is a strategy game, not Super Smash Bros, and you have teammates and a responsibility to play to win.
Tl;dr champion select is part of the game, counter picking is part of the game, getting counterpicked is your fault, fun picks aren't so for your teammates, complaining because you can't counter Kalista as Darius is your fault for picking Darius when they did or could pick Kalista.
, for instance, your best bet is that the player is bad. 
, OTOH, should never be blind picked. This is what I was referring to.