Why is there such a controversy??

So I've been noticing a lot of different opinions on posts about " can a glass of wine hurt my baby while being pregnant" and i see so many different anwsers about how a woman's doctor said hell no but then another women will comment " my doctor said it was ok " . What's the real anwser ? Like why are 2 different OB's saying two different answers? My OB told me that any amount of alcohol  ( even one or two glasses of wine ) could potentially harm the baby and not to do it. But I know other women who's OB have told the opposite .