Too many people using the paper-man fallacy.
First of all, there is a large continuum along which you have "mothers who drink"
If the people you're protecting are the unborn babies of alcoholic mothers, then prohibition is a poor choice of tool, and probably won't be very effective.
If the people you're protecting are the unborn babies of mothers who have a glass or two of wine every so often, then you are being a self righteous busy-body and you're being disrespectful to women.
but aside from that you know you cant just swap in the words "gay marriage" into any debate and say "I win!".
I tend to do that here because most of the posters here will understand the idea of being bullied by a majority that doesn't know what it's talking about, via the comparison to the gay rights movement. If you read the posts from Miradadi and Imelda, you see they refer to Women's rights and it "being up to the individual".
The issue always boils down to the individual's respect and freedom. It's easy to forget how bad it feels to have people talk flippantly about "your rights". But so often people seem to immediately forget this when it comes to talking about other people's rights.
"yeah, as a gay man I hate it when chat show hosts dredge up the "gay rights" topic and throws it around to get 15 minutes of yakking out of the way, now, let's get back to discussing if it should be illegal for women to drink while pregnant"