If the OP hadn't named the airport but had asked us to guess ARN would have been my call. I didn't have a hostile experience there, but it was much more extensive that anywhere else in the EU (and even in the US). Wanted to see every hotel reservation for the trip. 'Why are you changing hotels for the final night?' 'Can we see your return ticket?' Sweden is one of the few places where I still make sure to have everything printed off as their instinct doesn't seem to be to take people at their word.