I'm going to leave the door open
Why will you leave the door open?
I can prove to my friends that I didn't steal anything.
You really should close the door in a shared space. It's rude to just leave it open just to prove a point.
It's better than locking the door and they need to see I am not a thief.
This is a communal area and leaving the door open invites someone else to steal something. This is inconsiderate to others and you will end up getting the blame anyway even if you didn't steal anything.