I like this conceit. It's a nice sci-fi horror way of finding an excuse to do the nasty to a string of cuties, and explore the dark side-effects of that policy.

I would say too, that your critics are correct about the logical holes and lack of plausibility of this universe, but honestly that doesn't matter at all.

You've described the relevant parts of the universe concisely - enough to let the reader be pulled into the fictional world - and then you get straight to the sex and gore. Perfect!