For the blast, they stand up for themselves if they have someone else with them to help and for the quick poll tell a teacher or authority figure.
I like ya cut g *slaps head*
They make the message of the song direct and purposeful.
The short lines and repetition in the song make the message very direct. It is clear that the speaker of the poem wants his people to be let go. If the lines were long and very detailed, the listener would need to spend more effort to discern the singers message. The shortened lines give the song more power and emphasize the speaker's message.