My 7 yr old had a habit of greeting a meal with 'but I wanted 4 potatoes' 'but I wanted the sauce and meat separate' etc. Rather than just 'thank you' which I expect. This has now changed because said meal was removed if met with complaints or sulkiness. However, mil doesn't seem to think it's a problem. Dsd, aged 8, greets every meal with 'yuck I hate that/that looks revolting' etc when at mils and mil says nothing but thinks it's ok because dsd thanks her at the end of the meal, even if she's eaten nothing 
Aibu to think it's rude behaviour and continue not to allow it in my house? Mil thinks 'children are entitled to their opinion'