Well, that it's rare should be reason enough to accept it was a valid reaction. Either you were on a hair trigger for some reason, or there was a real threat and you sensed it.

The important thing is, what you did was, at worst, annoying. You didn't sic the cops on him, or threaten him, or whatever. The worst, the absolute worst, that your actions could have done, is made him feel annoyed that you didn't believe him about being safe.

He might have been drunk/stoned/whatever; that might have been both what made you nervous and what made him act the way he did.