Nero had nothing to do with the Romulans of Spock's 23rd century, so why would what he did affect Spock's attitude towards the Romulans of his time? Would that even be logical? It would the the ecological fallacy, really.
That said, I'd think unification is a moot point, anyway with only 10,000 Vulcans left around to be unified with the Romulans. Even with a sustained sci-fi like population growth of 25% a decade, it will take over 100 years for there to be even 100,000 Vulcans.
For what it's worth, the same can be said for unification in the Prime universe. After the destruction of Romulus, it's a moot point. Except in that universe, the political and social climate is probably far more conducive to the Vulcans offering the surviving Romulans a place on Vulcan than the Romulans offering a home to surviving Vulcans in the JJVerse.