So the AI pops up a dialogue telling me to beat it or declare war.

But I'm not in his territory.  Nope.  Not one unit.

So I say 'Okay I'll get off your land, are you happy now?'

Several turns later he bugs me again about it.  This time he has a rake and he's waving it menacingly.

And I say, 'Seriously, I'm not on your lawn.'

And so on and so on.

There is a patch of land around an outpost which is lit up as though I should have line of sight from it, but it's not my outpost, it's his.