nolongersurprised - Zebra fish? 'Badness'? Really?
Seeing as you earlier dragged thalidomide into this discussion you should be aware of one of the big lessons learned from that dreadful tragedy: the results of animal studies cannot be reliably applied to human beings.
I'm not sure why the radiation analogy is relevant
That's because you're being obtuse 
If there is no safe level of alcohol exposure in pregnancy, and there is no safe level of radiation exposure in pregnancy, why is the precautionary principle uncritically applied when it comes to alcohol but not to radiation? Why is it ok to tell women not to drink at all in pregnancy, but not ok to tell women not to fly at all in pregnancy? Better safe than sorry, surely?
As has already been pointed out several times, pretty much nothing at all can be proven 'safe'. There will always be some uncertainty. The choice of where to apply the precautionary principle and where to have a more nuanced and balanced assessment of risk is largely political. It's one way in which this principle can be abused. It occurs to me that radiation is not as much fun as alcohol. Neither are household cleaning products or emptying the cat tray.
Another way of abusing the precautionary principle is failure to examine the risks on both sides - in this case, the risks of telling women that there is no evidence of harm from low alcohol consumption (and obviously clarifying what we mean by 'low'), versus the risks of telling women that any level of drinking at all might be harmful, we just don't know!
You and RebornSlippy have done a great job of pointing out all the slight, potential, unknown risks of even low levels of alcohol consumption but you haven't acknowledged at all the risks on the other side of the equation, even though they have been mentioned several times now.
We know that many many women drink in early pregnancy, sometimes substantial amounts, before they realise they are pregnant and a lot of women get extremely anxious about this, and the harm they might have done, largely because they are bombarded with the sort of stuff you are posting. We also know that anxiety itself can have negative impacts on foetal development.
Alarmingly, BPAS have become 'greatly concerned' at the growing number of women who approach them seeking a termination because of unfounded fears they have harmed their baby through drinking in early pregnancy.
What would your advice be to those women?
Another big risk is that if people can clearly see the risks are being massively overblown, they will be less likely to believe any of the health advice they are given. Public health bodies will gradually cease to be a credible source of advice at all if they continue to put out over-cautious, non-evidence-based advice. That time your MW told you to quit smoking? Maybe that's bollocks too.