I created couple of custom malevolent aggresive factions. We had really bad relatons from start, I had a couple of messages that indicated for war, but there was no actual war. The strange thing is that their ships started following my units, as they were trying to attack them. Another strange thing is that on UP meetings info windows said that we're at war, but we weren't. Also not other factions weren't at war too. I post album with screenshots. All the wars presented were started by diplomatic actions.

http://imgur.com/a/jA8ej

Update: In diplomatic window, when demading that faction goes to war, faction A shows that is at war with faction B, while faction B can say that is with good realtions with faction A.