There's a difference between defeatists, no vote trolls, and logically voting on surrenders.
If the player gives up after 1st blood, someone misses their ult, when their team is clearly winning etc, that's a defeatist.
If the player is voting no to surrenders in a 4v5 or when one player on the other team has been able to 1v5 for the past 10 minutes, that's a no vote troll
If the player wants to surrender because the enemy Fizz can 1 shot your full MR tanks/doesn't want to surrender because we have supers flooding their base even though we lost a fight, that's someone voting logically.
You're not being held hostage if the game is actually winnable. You're being an asshole if you're voting no in games where you're losing so badly your team can't actually play the game.