Roles issue

We just started TSG. My son is very respectful outside of the house but with me and my husband he’s the total opposite. We were talking about roles this week and he said he disagreed with us being his teachers. He said that he didn’t really see any reason why he would owe us any respect, and I didn’t know how to answer that. I just said, because we’re your parents, but that didn’t seem to be enough for him. How would you answer that? He’s my biological child and he was adopted by my husband. They don’t have the best of relationships and my son often complains that he didn’t choose to be adopted by him. I think there’s some resentment there that sparks some of the rebellion and disrespect. My son is also adamant about not following Bible teachings so telling him because God says is not an option at this time. Please help.