Malice should be the default assumption in some scenarios. If a man with a covered face dressed in all black is discovered inside a bank vault, it should be assumed he was there to burglarize it. Maybe he was actually a ninja haplessly teleported through space and time by a powerful evil mage and landed in the bank vault through pure coincidence, but probably he's a burglar.

This isn't a court of law. We aren't morally obliged to feign naivety. If this wasn't meant to be a back door, they're free to explain their actions. But until they've done so to my satisfaction, I for one will assume malice.