It's wrong to not be honest with a roommate.
Mack ate his roommate's sandwich in the fridge and is now confronted by his roommate about it.
Mack wants to respond to his roommate.
Mack admits he ate his roommate's sandwich and offers to replace his sandwich.
Mack repeatedly denies eating his roommate's sandwich and even states he never saw a sandwich in the fridge.
Mack's roommate forgives Mack, and they enjoy a nice meal together.
This incident created a rift between Mack and his roommate that was never resolved.