A bullet does not signal any form of terrorism. What can you possibly do with one bullet without any form of firing it. Also, he hardly detailed how to revoke your citizenship; it was just one sentence. I guess I can understand how these agents would not understand the intellectual curiosity of a trip to this part of the world.

Cartridges[1] are prohibited on planes for good reason, I think. It is possible to set them off accidentally, and once you have a cartridge, building a one-time use zipgun is relatively simple, so if you want to keep firearms out of an area, you really need to keep cartridges out of that area.

Of course, if the bullet was really just the bullet without the propellant (that was not clear to me) then yeah, I agree with you.

[1] I think It's the explosive powder that matters here. A bullet with no propellant is just a lump of lead, which I think would be okay.

But he had already gotten off the airplane, and it's a lot easier to cause damage with a single bullet on an airplane than it is to cause damage with a single bullet while leaving an airport - so either he's so stupid that he'll carry the bullet onto every airplane, waiting for the chance, or he just forgot that he was carrying it, as he said.

One person has the bullet, another the firing mechanism, etc. Seriously, why does someone need to have a bullet in their pocket to travel on an airplane? They don't, so when an agent sees one, it's suspicious. It doesn't belong and raises a flag, just like some of the other articles in his possession. Enough flags and the agent needs to investigate.

If he were carrying it on his person perhaps, but it was mentioned that it was in a pocket of pants in packed luggage. Considering the proliferation of bullets in the US, smuggling them in one at a time in your stowed luggage seems a little inefficient to me.

Hit a bullet hard enough with a hammer or other hard surface and it will (at least sometimes) discharge.

No. Hit a cartridge hard enough and it will go off. A bullet is just a component of that cartridge, and it's completely harmless without a casing full of powder surrounding it.

Sorry, you're right. To a layman, though, a "bullet" usually means the whole shebang.

Coming home from Pakistan with a bullet in your pocket does point to the possibility that while in Pakistan you were dealing with weaponry. The guy doesn't give enough context to understand how the journal entry actually looked.

From your last sentence, I can see you are no stranger to making snap judgements without all the details. ;)

Wow, you travelled to a warzone and you dealt with weaponry. Clearly you're interested in expanding the warzone.

Well, it's possible that you were undergoing weapons training and stupidly forgot you'd left a bullet in your pocket before packing up. And it's also possible that a child gave it to you as a gift. This guy wasn't arrested or jailed - he was treated with not entirely unreasonable suspicion.