So tired of my husband's family

I dont understand why people think its ok to tell someone how to raise their child. I understand my mother in law is my sons grandmother but shes always trying to tell me what and how to raise him. When I tell her respectfully that I know what im doing with my child and how i would like to raise him she gets mad. She always calls me stuck up when i tell her don't give my 2 YEAR OLD soda or candy... I do let my son have a candy here and there but not much i rather fruits but soda no way in hell.... So for that im stuck up ... I read to my son since he was born and she and my sis in law that has a 3 year old called me dumb but now that they see how smart and good it is for a childs learning she started doing it.... But today i had it because she embarrassed me in front of people by calling me stuck up and that i think im better than people because i told her once again not to give him soda. She continued to say my other grandson ( the 3 year old) drinks soda and eats candy and that hes fine but, I dont see how hes fine when his mother came back from the doctor she said the doctor said hes well over weight but i dont say anything cause its not my child to comment on . I told her respectfully what your daughter does with her child is her problem and what i do with mine is my problem and that people parent differently .... They litterly give this 3 year all the soda and candy he wants and i dont want my child eating like that because diabetes runs in my family badly and i want him to have a healthy diet from now to prevent that in the future. .