Fine, they're still kids and one would still have to be a psychopath to slaughter them as he did. People don't carry hunting rifles on them for self defense and didn't it take the police 40 minutes to get there? Had Norway recognized self defense as a legitimate reason to own a gun and allowed concealed carry permits, the result might have been very different.
CCW seems to be on the most part ineffective against acts of terror look at 9/11 and the Oklahoma attacks. This particular monster created a massive car bomb as a diversion drawing Oslo armed response units into the city ready to respond or counter possible further threats. A fairly logical and coherent spree killer or terrorist would take CCW into account and plan their attack accordingly without diminished results. As always the predator has the advantage.
9/11 and Oklahoma? Penicillin won't cure cancer but that doesn't mean it's useless. CCW would have been very effective in an isolated area where a shooter had 90 minutes to shoot defenseless people at his leisure.
As a discussed in my post any logical and coherent killer would take CCW into account and change their plan of attack. The killer could have planted smaller explosive devices to maim and bottleneck fleeing victims or attacked at night using a suppressor on his weapon (legal to own in the EU). I don't rule out CCW as a reasonable step to preserve ones life but if somebody has designs on your demise then the odds are normally stacked heavily against you. Just remember competent armed and alert people die somewhere on this earth every day.
Of course an attacker has the advantages of surprise and prior planning but not every psychopath is an army of one who will expertly analyze the terrain and pre-place explosive devices undetected at optimum locations, etc. The other side of that coin is, all contingencies can't be planned for and plans have a way of falling apart, especially when you don't know who else might be armed.
They were not just random people, they were the future political leaders, union leaders, government bereaucrats, CEOs/board members of government owned corporations in Norway. ABB has claimed he intended to get there a few hours earlier, when the former prime minister visited the island.
Regarding CCW, there was an off duty cop on the island, but he was not carrying and was killed. On duty cops in Norway, must get permission from their superiors before they can arm themselves.