These are remarkable verses and not what we would expect today. The apostle appears he give no comfort to slaves, but only sets responsibilities before them.
Are Christians setting themselves up to be taken advantage of? To some extent, yes. That is not something unusual for the one who is ready to lose his lives for Christ’s sake in order that he may find it. There is something more noble than insisting on rights, and that is to demonstrate grace to the world. Grace is something which is unreasonable in the best sense, and it is something that is in very short supply in the world. Consequently it has great testimony value. The converted slave was to be thinking of his testimony much of the time.