Do people really think this behaviour is helpful?

Victoria
Elderly lady in a supermarket cafe watched as my 2yr old had a tantrum as he didn't want to share a piece of cake with me. Then the lady said 'are you his mother?!' 'He really needs to learn to share or he'll be ruined for life!'. She went on to add 'was he born in March as Aquaries children are known to be difficult'. I almost cried but also could have shouted at her. Did neither just stared in disbelief and waited for her to go away