executing a lord for pillaging a village would not have been considered justified back in the day in most circumstances.
Depends on situation. And Lord. And political stance. And many other factors.
Also, only Christian lords would be granted the honorary captivity and rights of war. Muslims and Mongolians (Read Aserai and Khuzaits) were considered as barbarians and would be executed. Vikings also had different standards and so on and so on. It was never black and white. And if one lord pillages your villages over and over again, after you captured him few times and released, coming back for more and more, no one would blame you.
It was never black and white and all this code was depended on very particular circumstances. Escaping from captivity would also justify the execution. Some lords being captured were held on their word and not even locked away. There even were cases when lord would be sent to bring back the ransom himself and they WOULD. Because they gave their word.
The simple game like this can't emulate all those situations, hence why it's important for traits to function. If lord does dishonorable thing by pillaging the village, you shouldn't be penalized for executing him/her. There should be some manner for repercussions.
Being honorable or dishonorable should mean something.
For example, being dishonorable would be profitable for all the pillaging, but if you go that way, you risk being executed. At the other hand, being honorable might prevent you from raiding, but in return you could hope that if honorable enemy captures you, he wouldn't decapitate you.
It's simple game so it needs simple solutions and if it has traits system, they should mean something.