Hi, M.. Aren't they adorable when they're so strong-willed? Wait until he becomes a teenager!
Have you tried the appliance locks that are sold in the child safety section of your local hardware store? They're also available online and I believe a prominant company is Safety First. That way, only someone tall enough can unlock the refrigerator and have access and your 2-year-old will have to find another outlet for his battle of the wills with you. I highly recommend the fridge lock and your 8-year-old will still be able to operate it and have access to the fridge.
By the way, I am a proud mom to a 145-year-old son, 13-year-old step-daughter, 11 1/2-year-old daughter, and 1-year-old daughter so I am a bit familiar with this subject.