My issue is that surely the same reductionist arguments that apply to ID - i.e that the phenomenon can be better explained by chance and the laws of nature - must also apply to human activity.
Must it? If there's any doubt about who makes iPods, you can go to the Foxconn factory and see them be made:
(Happy to be off the rice farm, or grimacing at the prospect of another 16 hour day assembling our electronic detritus? You decide.) "Reductionist" or not, why should we ignore this direct evidence of "intelligent design" of iPods? Now, on the other hand, the only intelligent agents I've ever seen create life have been human beings. I've never seen a god or an alien or any other "intelligent designer" construct a bacterium. So why should I believe that it happens?
We are foolish to invoke an intelligent designer in any circumstances whatsoever whether talking about the natural world or other human beings.
We're foolish to invoke an intelligent designer under any circumstances except where it is the best explanation for what we observe.