I noticed two major (VERY major, unbalanced) sources of opinion bleed.
1. The clan lost their fief to the enemy in a war
2. The clan has a member who has been taken hostage
Both of these are apparently always the king's fault and the AI hate you with a burning passion for having lost a castle they left half empty to go to the other end of the map randomly.
It's very hard to take the rest of your post seriously though, with the level of knowledge we have on the process suggesting people to fire is just plain dumb.