The other day some terrorist in France ran a trailer truck through a crowd for a mile or so, killing about 80 people. That's pretty big, not necessarily involving any plans, nothing illegal, and no weapons. (Though in reality a larger attack was planned and he had weapons in the truck). Basically, if people really want to kill each other, they can.
This reminds me of the old constraint on science fiction universes: "Any interesting starship drive is also a weapon of mass destruction". Thus, if your interstellar civilization is going to work and be at all peaceful, it better have some way of dealing with this. Looks like it turns out we don't need to imagine starships, or even airplanes, for this to be a problem. In the hands of sufficiently motivated terrorists, everyday tools like trucks become weapons of mass killing. There are a few approaches to the problem:
Ban or restrict any tool that can be used as a weapon. This is infeasible in the case of trucks.
Strongly vet and restrict who can get their hands on powerful tools, like trucks. This can be a real pain and damper on economic activity if the licensing gets too fine-grained, and doesn't really work in the case where you have mixed licensed and unlicensed actors running around in the same space, and want to be able to leave powerful equipment lying around for convenience.
Strongly vet people who are to be allowed in your society to make sure they have good intentions, and make sure there are no all-out social conflicts that might drive someone to crash a truck into a crowd at high speed. This solution works best, but can be harder to achieve. If you have existing social conflicts, they can prevent this solution.
Take an extremely harsh group-retaliatory approach to large attacks so that no social faction has incentive to act out.
Surrender to the coming darkness, and watch your people die.
Every realistic society must use some combination of these, depending on the particular costs and benefits in individual cases. This of course requires a wise and powerful government.
1 (ban) and 2 (licensing) are pretty unrealistic in this case. Especially as a solution to 2, which involves answering the question "who should not be allowed to drive a truck?", can be much better applied to 3 or 4.
The answer of course, is that the West is in a state of insecurity, trending to war, with anti-western Islamic State terrorists. This problem faction needs to be physically removed and restricted from any area that requires high general trust, like any Western country, or otherwise neutralized. To do so reliably however, the French would also have to apply these measures to anyone who thinks anything like them, because you really can't easily tell who is and is not an IS soldier. To do that, the French need to declare a state of emergency, institute martial law, and begin processing people for deportation. And to do that, the French need to defeat and replace the local branch of the international community that refuses to do anything and is bent on flooding Western countries with hostile foreigners and running interference for their acts of war. And to do that, the French need to find within themselves the will to act in self-defense. This has all been said before, the last time this happened. It will continue to be said again, because the French will continue to choose option 5 on the mistaken belief that predators will stop attacking if you aren't aggressive.
But we digress. The point here is that no amount of restriction of tools can ultimately prevent social chaos and determined enemies from causing trouble. It can certainly help, especially with the most dangerous tools, but when even transportation vehicles become instruments of war, the only robust path to a peaceful society free of hatred, is to actually win, and then enact harsher suppression of social conflict, harsher controls on social ideology, harsher restriction of who can be a part of society, and social and political systems in which, unlike in our own, terrorism is not a viable political strategy.