jens, 
This morning I'm reminded of a person I knew, who would treat everything as an attack, or the potential for one.
You might say "good morning" to them, and their reply would be a snapped "what do you want?".
It's rather difficult to deal with, because any reply to this would get twisted out of shape in similar way.
So what do you do? Ignore them? Seems like the only way.
Except... it must be hell to live like this. And nobody chooses this kind of hell for themselves. This is trauma...