As parents, we all make mistakes. Hopefully, we learn from our mistakes and guide our children in a way that will help them be successful.
Whenever you offer advice to a parent, you run the risk of offending or upsetting him or her. Is it possible that when you talk to your boyfriend about how he parents his daughter that he feels threatened or offended?
Parents can have different parenting styles. It is important that you two learn to communicate and reach a compromise with one another. While you do not share the responsibility of rearing his child with your boyfriend, you do share a home and life with him. Thus, your input and concerns should be taken seriously.
It appears that he is not willing to compromise with you. This leaves few options. So instead of focusing on his parenting skills, ask him what his expectations are for you. How would he like you to interact with his daughter? Does he want you to take on an authoritative role or leave all of the parenting up to him? Ask him to be specific with you so you are both on the same page.
Once you know where you stand, it is time to make a decision. Can you live with the fact that you disagree with the way your boyfriend parents and that he does not want your input? This will most likely not change. It has stopped being a problem and has become a fact. You need to either accept this fact or move on. Only you know what is best for you and can make this choice.