Sadly enough, "dominance" is too often abused as alibi for the lack of basic manners and politeness.
The greatest challenge for a sub/slave is to learn to differentiate between the responsible dominants and the "players".
It is the sub/slave/knight to in his own will and voluntarily ask for the permission to serve, and to ask for the permission to be granted to show the Lady's colors. On the shield, that he will then bear whilst serving unconditionally.