Before the smoking ban came into effect, many restaurants had smoking and non smoking rooms, so that people who didn't want to be around smokers didn't have to be.
I'm not even advocating that, just a room that mum can go off to for 5 minutes, which is nice and quiet so she can feed and other people can get on with their meal. Even if this wasn't to happen, what's so bad about a fucking napkin being used to obscure the view?
Although to be fair, why you'd take a baby of breastfeeding age to a fancy restaurant is beyond me.