Can I say something racist to a racist kid?
Are you serious? Why would you say something racist to the racist kid?
Because racists are disgusting creatures. They deserve to be insulted
While you have the right idea that racists are disgusting, you need to be the better man and not stoop to their level and use racist terms as well. You need to speak properly and with respect, while still maintaining your scolding to the person.
You are discouraging me from speaking the truth. You are on their side.
I am not, I just don't think it is okay to use those words even when speaking to racists people. Those that overhear you don't see as defending somebody, they just see another racist.