Ask

Well first of all I already said, there are more accessible options to kill people. Explosives are more for proper terrorists. And it's an extreme. Criminals shouldn't have access to anything (including information) which assists them in injuring people. And I think generally humans are born with empathy and feelings. And lots of them have ethics. In a working society and without being faced with existential threats, they're the exception.

More mundane and everyday scenarios are something like doxxing, ratting out people or leaking their secrets. Or you're the admin of a service and protect your users. Or you're and employee and protect the company.

I don't think it's any big issue that I (and some other people) read the old chemistry books. And we can make things moderately difficult by removing them from the shelves, so it at least takes some effort to get there. That should already help. It's the same idea like putting a small fence somewhere. With enough dedication and effort it can be circumvented, but it gets you somewhere. Of course that still doesn't address the criminals. So we need other ways to filter them out.

Edit: And I forgot safe-spaces. Some issues are better discussed in private. And it helps opening up when there isn't the general public and stereotypes involved. I guess that applies to science to some degree as well. Some studies and achievements are turned into misinformation or could be weaponized, so they might better stay within the scientific community. But that's not ideal.