In my current game I have encountered some aliens. Two races actually, one is living in wrecks, and have a bad habit of ramming my ships, the other is sort of "normal", ie. they fly around surveying stuff. The wreck people are out of diplomatic reach, which means war, when I get my act together.
The other aliens are quite friendly, they accepted my diplomatic overtures, and now I have a diplomatic relationship to them around 250 points, and I have just allowed them trade access. But their geological survey ships slow down the game to a crawl, whenever they are in or near my systems. So last time I had a visit, I decided to try out my brand new marine assault vessel. I hijacked their survey vehicle and took 18 prisoners, who were interrogated. A bit worried I looked at the diplomacy screen, expecting relations to have worsened, but no: It actually went up and is now around 300.
Question: What happened to the prisoners after interrogation? They were nowhere to be found. No quarters?
Question: Is alien races indifferent to their vehicles getting pirated? The rise in diplomatic relations could be the result of me granting them trade access, but certainly the hostile takeover of one of their civilian ships should at least balance out this rise, if not result in overall deterioration of our mutual relationship. Or is trade so much more important than pride and honor?