I am assuming a feudal type of society and a feudal notion of honour - wherein one swears on one's personal honour to serve a master to the best of one's ability. Perhaps even a society wherein there is a tradition of family service to the family of said master?
I hate this answer, but I think that such a person is honour-bound to serve even a dishonoured master to the best of his/her abilities even though such service would mean that that person should share in the master's fate/ punishment/ whatever. The Bible itself counsels such an answer when it advises people to honour shittened priests and the church traditionally held that absolution at the hands of corrupt priests was still absolution despite the obvious veniality of the vessel.
However, the oath of service to a master does not negate other oaths sworn - so a knight sworn to uphold right and justice is justified in defying his master as long as his actions do not harm his master's interest. I.E. s/he can defend a prisoner or captive from unlawful execution. Such an action would likely be seen as betrayal, however, and would result in said knight sharing the prisoner's fate.
Traditionally, those closest to a dishonourable leader have always been found culpable in that leader's dishonour, but the rank and file are usually not held to the same level of responsibility. Higher officers would lose their heads, lower officers would be imprisoned and fined, serving men would be imprisoned or whipped or just disarmed. It makes sense - one who is loyal even to the point of participating in dishonour could not honourably swear to be loyal to the opponent.
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I hate this answer, but I think that such a person is honour-bound to serve even a dishonoured master to the best of his/her abilities even though such service would mean that that person should share in the master's fate/ punishment/ whatever. The Bible itself counsels such an answer when it advises people to honour shittened priests and the church traditionally held that absolution at the hands of corrupt priests was still absolution despite the obvious veniality of the vessel.
However, the oath of service to a master does not negate other oaths sworn - so a knight sworn to uphold right and justice is justified in defying his master as long as his actions do not harm his master's interest. I.E. s/he can defend a prisoner or captive from unlawful execution. Such an action would likely be seen as betrayal, however, and would result in said knight sharing the prisoner's fate.
Traditionally, those closest to a dishonourable leader have always been found culpable in that leader's dishonour, but the rank and file are usually not held to the same level of responsibility. Higher officers would lose their heads, lower officers would be imprisoned and fined, serving men would be imprisoned or whipped or just disarmed. It makes sense - one who is loyal even to the point of participating in dishonour could not honourably swear to be loyal to the opponent.