How do I break up my mom and her scummy boyfriend?

I am white man and 17 years old and when I was 14 my older sister who was 19 was raped by a group of black men who were racist against white people and were part of some group that admired malcom x,the grand wizard of the black kkk.Ever since then my sister has been a mess and into drugs and goth culture even after the pieces of trash who raped her were thrown into jail.It left an impression on me because I always here about white people being so racist but I live in an area where black and mexican people are the majority and I am always called craker and white boy and blanquito and gringo and the victim of racism.My mom who raised me and my sister alone since my dad died in iraq in 2004 has been going with this black guy and I dont want him around my family.I am not racist but i dont like the idea of 2 people from different races being together.The other night i confronted him and I was like get away from my mom and he got all mad and called me a little white ***** so I called him the n word,not cause I am racist but because I was all mad but my mom got all mad at me cause I said that word but she didnt get mad at her boyfriend for being racist againt me! What the hell do I do man?