The only ‘badness’ that I can see about the robot slave theory is that it goes against so much of Scripture.
If God had had some of us be robot slaves picked at whim from the masses and the rest of us He flushed down the toilet, then it should make sense that way. There’s just too much evidence to support such a theology.
I agree, and am glad that Reformers do not believe in such a thing. The robot slave theory, as argued, was wholly invented by our critics and thrust upon us against our free wills. :) We reject it. Our position is that God is sovereign and in full control of everything. Within that dynamic we experience the freedom to sin, and to do good in God's eyes once saved. These experiences are fully real.
However, this idea has somehow been translated into the aforementioned theory. I am not sure whether this is done in order to persuade lurkers, or whether it is an instinctual reaction to any thought of man not being in control of his own destiny. The natural state of all of us at birth is to want to be in full control. So, theology developed that promoted man being in (ultimate) control, including a small group of elite who were in "super control". That is, they granted themselves the power to stand in God's place and speak for Him with the force of law (Latin).
I at least partially understand the need that this fills for a huge number of Christians. On the one hand one can be a good Christian, and on the other he can remain in control and have eternal self determination. I just don't think that's what the Bible teaches. :)