Because it's cooler to hate murdering Klingon bastards than murdering Romulan bastards?
And I guess because while the Kirk vs. Kruge thing was just personal, Kirk vs. Nero also doomed the guys washing dishes and keeping the inventory straight somewhere in the bowels of the Narada.
And it's never cool to hate. Because in the words of the noted philosopher Dalton, "No one wins in a fight."
I can totally respect this reasoning.
I typed up a debate answer to others, but I'm frankly no good at debating. So I'm not going to try.
In my opinion, Spock was Spock. In my opinion, Kirk was right. In my opinion, it was a good movie.
Kirk had no idea if Nero and his ship would survive passing through the singularity. If they did, and Nero resumed his attacks in another time period, he could be dooming further worlds and billions or trillions of beings to destruction. (In some other splinter timeline, granted). He gave Nero an opportunity to surrender, which was declined.
At this point, I have no problem with Kirk ensuring that the Narada would not survive his passage through the wormhole given Nero's demonstrated astonishing destructive tendencies.