Many varieties of cheese are commonly aged to add additional nuance and depth to their flavor. Aged cheese is frequently referred to as "mature". Young people throwing items at passerby is not mature in the sense that it is rude and impolite. Therefore if the piece of cheese they threw at the joke teller was not aged, their response to the act may refer to either sense of the word "mature"
I walked past a gang of youths yesterday and one of them threw a piece of cheese at me , which hit me on the back of the head . I turned round and shouted , ' ' That ' s not very mature ! ' '