Narrative Theory (Un-finished)

Attack the Block:

In the opening sequence of Attack the Block we see the the main protagonist mugging a woman at gun point with a group of other youths. The stereotype of anti-social teenagers are explored and used for comical effect. Although we know that in the end of the film the teenagers change their ways and save the day, until then the viewer has this negative perception of the characters.
The possible implications of this opening on the viewer are a biased and un-fair perception of all teenagers because
THEN THOERY THAT EXPLAINS THIS EFFECT...