I hate people who just casualy help themselves to other peoples food. Wtf. The way I was raised, going through someone elses pantry and fridge  was completely unheard of. You wait until you were offered something to eat or drink or you politely ask, unless they were close relatives and told us to help ourselves. I use to have these two friends who lived down the street and they would often come to my house when my mum was at work. They would just casually open the pantry, grap some noodles and start cooking them on the stove. Then help themselves to some cereal. I was a dumb preteen at the time and to shy to tell them off. Almost every day they would do this until one day I snapped and refused to answer the door when they knocked. Well they stood there for, I shit you not, 30 minutes knocking. You'd think they'd take a hint.