I think this is more believable than for him to argue with Kirk that he must be saved.
The character would have grown in stature if he had, and delineated and defined himself as distinct from Kirk. What we got is just a gratuitous "fuck yeah!" moment - it's okay, but not interesting or impressive in any way; it's a throwaway. One of the few things I didn't really enjoy about the movie.
Maybe a moment was lost. I'm wondering how the scene would've worked if it had been done the other way around. What if Spock had offered Nero rescue? Kirk looks at him like WTF. Then, what if Kirk had uttered Spock's line?
For Spock, it would've been the logical thing to do, not the emotional one given his story arc. It was probably regulations to offer rescue. It was logical. It would've shown he has decided to act like a Vulcan. It even would've even been (neatly) diplomatic for him to mention relations with the Romulans. It also would've allowed us to wonder what he was really thinking. Is this what he'd really
want to do? What's going on with him?
Kirk, on the other hand, could've gotten by with the "not in this case," remark because things could be read into the line, too. Either he believes it's how Spock really feels, but Spock won't do it, so he does. Or, he really means it. It lends much the same ambiguity to the line as Kirk's "let them die" line in TUC.
See, that's why I believe it was a plot hole, at least for Spock within the movie. He broke character. Spock is not sinister and vengeful. After all, this is the same Spock who didn't want to go after Nero in the first place just after Vulcan was destroyed.
With Kirk, my feelings may be based less of a plot hole within the movie, and more me projecting what we fans know about Kirk onto this one (who is, after all, the
same Kirk). That's another reason why maybe Kirk should've been the one saying, "In this case, no."