I really really dug this post about carrying gunpowder through airport security.
You can’t create a secure airport that is worth traveling through. The solution isn’t to figure out every possible way that people can attack airports and prevent those… That’s an insolvable problem. A better way is to find people who are trying to hurt us and deal with them in a legal, just way.
People who are trying to hurt us face many of the same problems we do. They need networks, support, materials, etc. They also recruit and are looking for moral support.
These seem like much richer avenues of investigation.