The principle problem with playing God in this particular context isn't that we must concede a "limited scientific knowledge" but that we don't do it very well. Placing a premium on minimizing "suffering" for example, works in a philosophical system where every element is negotiable but both God and nature - take your pick - have apparently failed to design it into real-world ecological systems. It is, after all, a somewhat ill-defined parameter - would it justify the extinction of all species of mosquito because they make itchy lumps on people's flesh and cause malaria? Would the starvation of members of species who depend on mosquitoes for food constitute suffering and hence dictate against it? Would mosquitoes themselves suffer? Does suffering depend on sentience? Apparently not, according to the Professor's misreading of Isaiah, but is there a gradient? Do a thousand mosquitoes writhing in their death throes as a result of a good dousing with DDT offset the suffering of a malarial child? Does the life of a cow justify the suffering of plants torn from their roots in their prime? Is it really the case that a rat is a dog is a pig is a boy?
And that's the reason we don't do this sort of thing very well. Controlling an ecological system based on ill-defined ethical parameters would be a great experiment but not one I'd imagine it much fun to live in. Cold that constitute an ethical experiment if it resulted, however inadvertently, in the sine qua non of the Professor's control system, suffering?
We have reached the point of silliness, actually well within the first paragraph. But this one serves to indicate how muddled the Professor really is on the issue:
The second response to the accusation of playing God is simple and decisive. It is that there is no deity whose prerogatives we might usurp.
That, unfortunately for the Professor's case, is an absurdity. One can "play God" in the absence of the existence of God just as one can play Buck Rogers versus the Aliens in the absence of the existence of the latter. And probably just as well. "Playing God" in this sense isn't a theological term but the description of the activity of setting up an alternate ecology based on ethical precepts. One might as well design a sewing machine around ethical precepts, and in fact, it would be much easier - we actually do know how a sewing machine works.
Most excellent analogy, Bill! The same, BTW, is true of our attempts at tinkering with human society. We don't know how to engineer that either.
The Precautionary Principle, a favorite of liberals, would actually be the ultimate in conservatism if applied consistently.