I've seen it in a restaurant and it was right in my eye-line, and she wasn't particulary discreet about it and yes, I found it wrong.
The trouble is, some women as soon as they pop out a kid become 'professional' mothers and feel it is their right, nay duty, to ride roughshod over everybody else's feelings, this can be by not removing a screeching kid from a shop, to changing a sh1tty nappy on a bench in a shopping centre (yep, seen that to) to indiscreetly breastfeeding.
Discreetly breastfeeding a baby is one thing, but flopping the old lills out willy nilly and whereever they feel like it is something else altogether.
And mouth or not mrs-overall, if you butted in on a discussion I was having with a women with her udders out in a restaurant, you would swiftly and in no uncertain terms be told to mind your own - I've got a mouth on me as well.
The mother of my children never found it necessary to do any of the above, and whilst I fully understand and accept that every parent loves and adores their children and they are very very special, they are not particulary special to other people.
I have lost count the number of times I have been in a shop and there has been a child screaming at the top of its lungs and the parent just smiles indulgently at them - when the polite thing to do would be to get the kid out of their and calm it down.
So, to answer the question, I would say no, if it is discreet and yes if it is not.