Why doesn't anyone seem to have a problem with Spock being pretty willing to let Nero have it?
Because, right from the beginning, the Vulcans have always been a pretty ruthless bunch. Consider:
As pointed out earlier, Spock was urging Kirk to kill Gary Mitchell as early as the second pilot.
Amok Time: In the first major "Vulcan" episode, T'Pring plots to have either Kirk or Spock killed so she can be with Stonn. And even the sainted T'Pau forces Kirk and Spock to battle to the death for the sake of tradition, even when it's obvious that Kirk had no idea what he had just agreed to.
Journey to Babel: Spock admits that his father, Sarek, is perfectly capable of killing in cold blood--if he has a logical reason to do so.
In other words, pretty much every time TOS did a "Vulcan" episode, they made it clear that the Vulcans could be dangerous if crossed . . . .
like maybe if you destroyed their entire planet?
To be honest, it often seems like people who have issues with the new movie have selective memories (and rose-colored glasses) when it comes to what TOS was
really about. Or maybe they grew upon TNG instead . . . which was much more heavily invested in the idea that Trek was supposed to be some sort of visonary blueprint for the future. As opposed to TOS which was more of a rough-and-tumble space opera filled with flawed, volatile characters who weren't always paragons of Starfleet virtue.
Just like in the new movie.