What’s naive about that is that, yes people decided to kill people — and if they hadn’t, life would be better — but how should we stop (or at least reduce) the loss of life?
Can we stop these people from thinking what they think? Well, they are crazy nut-jobs — so that’s unlikely!
Can we stop them acting on those thoughts? Maybe. By handing them an easy way to turn those thoughts into actions (easy access to explosive materials, guns and ammunition, for example), we’re making it easier for them to turn their thoughts into deeds.
If we could prevent them from getting hold of such dangerous things, they’d have to resort to more primitive ways of carrying out their thoughts — knives, bows and arrows, that kind of thing. This would reduce the rate at which they could kill people — give more people a chance to escape, give them a better chance to defend themselves — and give law enforcement more time to handle the situation.
So, yeah — it takes people with bad thoughts to kill people. But that in no way changes the fact that denying them the means to turn thoughts into action would be helpful.
That’s why we have airport security — not because “People kill people — planes don’t fly into large buildings and kill people!” (which would, presumably be your argument) but because “People with bad thoughts can use a plane to kill people”. There is no logical difference between denying terrorists access to the cockpit of a 747 full of aviation fuel and denying them access to guns.