No one is saying its ok to drink while pregnant, there are many things that you can normally do that you shouldn't do when you are pregnant. Fly for example, or engage in extreme sports like skiing. Similarly, you should not drink prior to driving, in the same way that you shouldn't be texting on the phone, or be sleep deprived when driving.

You can be gainfully employed and meet your social responsibilities while having a beer or two on a Friday evening, as the majority of people are able to do.

I've never heard of this myth about the alcohol evaporating during dinner, so I won't comment on that - when I drink alcohol, I do so because I intend to consume said alcohol.

As for the potential for addictiveness, there are many things in life that certain people are not able to handle well, with ruinous effects on those people's lives. Unhealthy junk food for example, or even something seemingly innocuous like the ability to invest in the stock market. I tend towards the philosophy that we should not have the government ban those things, especially when the vast majority of people are able to enjoy those things responsibly. Certainly we can provide additional resources as a society to help those people, but lets not ban it for everyone else.