He is trying to engage you. Don't react at all. Just look at him very deadpan and say something like "I can't hear you when you talk to me that way" and then walk away.
I have 4 children under 6. Disrespect is not an option, like wearing a seatbelt or playing in traffic. I will either not listen to it and walk away, BUT I mostly stand eye to eye and say "you will not talk to me that way". Change your words. If she doesn't there is a punishment. i require this of my 20 month old. you have a harder road to repave here because 6 is an older age. Hang in there and don't budge an inch on what you expect. no way. you are the mom.