Plz help.My ex is mean to me how tos top him!?

My ex is always mean to me & idk why i never done no S***.In FB this how our conversation went like Him:Yup shes a dumb slut. Me:looks whos talkin & i aint a slut. Him:sure u r a ho ho Me:if you got to tell me somthin well atleast say It to my face Him:u scare you wont do crap cuz u know my sis will beat your azz Me:No duh & was i talkin about beatin you up or somethin...NO.So you should shut ur mouth Him:U were afraid to talk to me when we went out & i always tried to talk to you scary ***** suk a d**.(why did he bring our past in this?).Im going to say this."omg why the *** are you mean to me?what did i ever do to you?huh(& "watever" i did to you well im srry!)you know what forget it.Im not gonna sit here & argue with you.You allready did to much **** to me & im not gonna take no'mo."Is this a rite thing to say so we can stop arguin or make him think alil!?Cause seriously i dnt get it he is the one who cheated on me & cause the break up!why does he act like this why he mad with me!