If someone knocked on your door, quite unexpectedly, in the middle of the night, can I err on the idea that you would be quite panic-struck?
But if humanity got a signal from another civilization tomorrow, do you think it is safe to err on folks being quite happy?
Quite likely, but only because the socially acceptable reasons to knock on someone's door in the middle of the night are usually something pretty bad. I wouldn't fear that they're attacking me. I would fear whatever they are waking me up to tell me about.
But if a stranger knocks on your door in the middle of the day you might just open up and say "no thanks, I don't want your pamphlet/vacuum/encyclopedia".
I mean, even if a stranger knocks, it seems weird to kill them assuming they're dangerous, even if we have "don't let a stranger in" etched in our collective consciousness.