In Chapter Four, why do Long and Tate pull Bri out of the security line and throw her to the ground at school?

In Chapter Four, Long and Tate ask Bri to give them her backpack so they can search it, and she does not want to do this because she is selling candy to students at school, which she has in her bag and is against the rules. Critically, Bri and many other students at the school think Long and Tate target black and Latinx students more than white ones for security measures. Bri also asserts that the security guards use excessive force on her in throwing her to the ground.