Answer:
First of all, God I love this book. It's so good. SO good.
Anyways, for your answer. The media is "charging him with his own murder" because they're basically saying that because he'd made mistakes, he deserved to die. They believed that Khalil had dealt drugs, and thought that because he'd dealt drugs, he somehow had it coming.
Yes, Khalil had made mistakes in his life. No, he did not deserve to die. Everyone has made mistakes, and noone deserves to die because of them. Life's worth has no equal, and Khalil's mistakes did not atone for his death.
A lot of the reason the media believed this was because he was black. In the eyes of the media, if you happen to be a minority and you have made mistakes, murdering you is pardonable.
Because they thought Khalil basically deserved his death, noone would help him. Basically everyone except for those who knew him or who understood, just turned a blind eye, or blatantly took the side of the officer who'd killed Khalil. They'd said that the officer had done right, taking a "criminal" out of this world, even though Khalil had never hurt anyone.
I hope this helps!! Just ask if you need clarification or help with anything else about The Hate U Give.
