I think that you're missing the point. The prolem is not that he was interrogated. It's rather how he was interrogated and how the agents conducted themselves.

I think that you're missing the point. The prolem is not that he was interrogated. It's rather how he was interrogated and how the agents conducted themselves. They treated him like a spy and employed some psychological techniques. Was that even necessary? Doesn't e deserve to be treated with respect? Why did they immediately assume he was a criminal? Especially when they knew the machhines were defective? Considering the fact that they knew the machines weren't perfect and that household items set them off, they should've considered him innocent until proven otherwise and treated him with respect. Even more so if he's a citizen. They should've atleast told him that "hey, the following items could set it off, have you used one of these?" They could've then verified his claims with the chemical that showed up. All this will only become obvious once it happens to you I guess.