Why do people get abuse for having the odd small gl of wine whilst pregnant?

i'm 3 months pregnant and have had a small gl of wine twice since i found out. my midwife said its fine to have the odd drink or two every now and again (although i don't think i would have two in one day.) i was curious about what other people did/do whilst pregnant on various forums (including this one) and saw a lot of people geting vicious abuse from people because they too had the odd drink and had healthy happy babys! i just wondered why people are like this to nice, normal people who just happened to have the odd (medically allowed) drink? also, i came across this with drinking cola and eating chocolate (which i have also done a lot of as I have had horrible horrible sickness and cola is the only thing that settles it and i've been craving choc like mad and eating it helps me not be so emotional! lol) I was just curious if there's any real definitive research that i have missed as I've heard all the conflicting medical results/advice from now and over the years. This is just out of general curiousity and wondering what other people's views were and if anyones been "told off" for doing any of these things?