Spock never recovered from losing his world and mother. Thinking he got over it is totally misunderstanding his story arc. Listen to what he says on the trip to Kronos and you'll see.I am sorry but I just don't buy it. Spock lost nearly his entire race plus his mother and yet he recovered pretty fast. Here he loses someone he's known for a little over one year, that he even didn't like for part of it. Plus he's a Vulcan for God's sake! That cry was just too much!
Remember, Vulcans are taught to act unemotionally. They all feel. And the reason they act unemotionally is because beforehand, they very nearly destroyed themselves in nuclear wars. Even Tuvok, the "straightest" regular Vulcan character in Trek, refused to repress his emotions during his childhood and he lost his temper in "Random Thoughts"
All that said, Spock yelling "Khaaaaan!" was cheesy. I'd have preferred a smouldering fury, and the scream as a challenge once he beamed down to San Francisco and laid eyes on Khan.
I am sorry but if we use old Spock as a reference for judgment. As far as I know in all TOS he only acted mad and angry TWICE and in both instances he wasn't in his normal state. The first time was during Pon Far which is an exceptional phenomenon that only happens once every seven years and that the Vulcan keep a secret because they are somewhat ashamed of it and the second time was when he was regressed to an earlier form of his race by the atavachron and that's also something exceptional. Other than that we never see spock lose his cool one way or the other for the entire series. Current spock seems to lose his at the drop of a hat in comparison.
Something is not right here.