This seems like a perfectly reasonable reaction. Forced to clean up our leftover food every Friday? THIS IS NAZI GERMANY! I didn't know Godwin worked a desk job.
The thief helped the lunch owner dodge the TB bullet. They should be thanking them. :-)
Also, I can't imagine how serial lunch thieves wouldn't expect to contract a communicable disease eventually. Sooner or later their crimes will catch up to them.
There's a Greg in our office, and this flowchart would work perfectly for him. Except it would be placed in front of the coffee, and instead of asking if he has permission, it would ask "Did you make the coffee? Have you ever made coffee? No? Then go away."