A slave is whoever accepts, in order to survive, to follow other's will (other's laws) as if it is his. Obviously a slave's follower is also a slave.
Jesus' message was simply addressed to the very few beings who doesn't feel the need to be a slave in order to live among others. In other words, a real christian has, therefore, no law to follow but the unconditional Love toward others.
Could one imagine Jesus living as a soldier, at any position, submitted to a law?
Could one imagine Jesus working as a judge or lawer limited by a set of laws?
Could one imagine Jesus as a politician whose job is to address the masses with anything but the truth?
Could one imagine Jesus being a Jew, a Church believer, a Muslim, that is, obeying some divine laws other than loving others, friends and enemies, to no limit?
Where there is justice, there are slaves.
Even who are preparing the next world war by dividing people, since a decade, in so-called opposing camps are themselves slaves as the Great Hitler and his top officiers were for example.
The real master is the one who has the power to give good things to others without the need to get anything in return.
That is why the Ultimate Creative Power/Will can be seen as a powerful master by ITs great/unlimited LOVE only and nothing else, because all other aspects of power are meant for the slaves who have to fulfill their pre-programmed roles... (like Pr Bush has commanded during 25 minutes all US forces not to move to protect NYC from the second hit on Sept 11, though at the same time he expressed clearly on TV that he has doubt that the first accident could be an attack coming from the end of the world! But who cares! Because if the truth is known, the victim families won't get their promised big money from US system).