Even if you're first pick. 
My question is, what can I do? I don't want to feed and troll, lose the game for 3 more people and getting reported/banned, but I don't want this person to have any pleasant memories about this game. And surely I don't want to play another champ and, importantly, with this teammate.
How do you cope with such attitude?
Don't declare what you want to play.
The main reason Jhin is getting banned is because your team doesn't want you to play him. It has be said by a lot of good that jhin is a bad adc. If you pick Jhin you team has 0 sustain dps because he is a burst adc. On top of that not saying your bad at jhin but most players playing jhin first week are trash. It would be like if a player on your team hovers jg vayne. And you look up his name and find out he plays jg vayne with a 0-5 record, im sorry but I am banning vayne and if he trolls ill dodge.
If you want to play jhin hover any adc and say jhin is trash let them pick it and when the don't ban it then take it. Just make sure you play like a god or your team will prob blame you if they lose even if your doing good.
Riot should just make it impossible to ban a champion that your teammate declared.
Even if you're first pick.
Seriously contemplated banning from my teammates on a few occasions.
Keep in mind the length of time it takes to actually master a champion. Someone who mains a given champion probably has 40+ games on it, and if you're trying shenanigans like Jhin first week he's free when you're 4 allies are in tryhard mode with a main pick vs. 5 other players going tryhard mode with their mains, you're realistically putting your team at a disadvantage.
It's been proposed several times that new champions should be banned from ranked for the first week they're free: and preventing your teammates from picking the hot-new champion is a big factor as to why new releases tend to be heavily banned.
You're team probably also saw a lot of Jhin players making some pretty spectacular fails and really do not wish to have anyone on there team pulling those.
If it's in normals.. just dodge until it's not banned if playing is that much of a priority for you. The simple fact is people are constantly banning him in norms for nearly no reason. He's actually undertuned right now and kinda a detriment but that may be fixed by someone experimenting and getting to know him. There could be a optimal build a lot more powerful than the current inf edge + rfc + ess reaver core. (Make sure you ban Nautilus if you're jhin bot. He's a extremely painful counter. Worse than Leona Imo. Oh and never go into the game if the enemy team is 
)
The most hilarious part is the majority of the time in my games the enemy bans . They've even let first pick graves go through rather than have him ingame..
If it's in ranked, then you probably shouldn't be playing a new champion in ranked the first week or two it's released (Get plenty of familiarity with it first). However, if it's norms and riot doesn't bring back teambuilder, then new champions should be unbannable so people can play as and against them. With the current system everyone will literally just permaban any new champions for the first week to a month of their release.
There is a problem if you have to insta lock in blind pick in order to get any play on a champion outside of customs / bot matches.
Reasons that I would ban Jhin: It is a ranked game. Don't bring ANY new champion into ranked. I don't know much about them, you don't know about them, and the team doesn't know about them. It just leaves us with a huge questionable gap in competency for Ranked. Play new champs in Normals.
Riot shouldn't allow new champs to be used in Ranked for at least a month because it's competitive play and we don't need an untested champion just thrown into the mix. I dislike seeing new champs picked in ranked JUST BECAUSE THEY WERE RELEASED AND NOT BANNED!
