Must have been a big ass battery pack that it scared them so much. I know there is a safe limit within which battery packs are allowed to be taken on board a plane, so wouldn't they be working to the same specification?
It probably didn't even occur to them that lipos like to explode when hot / stabbed / dropped from great heights / crashed into ground at 100+mph* - all they saw was young lad with battery box and they lost their shit over it.
*Yeah, angry bee is no more, it suffered a rapid unscheduled disassembly over the weekend - twice.