It's personal, obviously. You must have ticked him off in the past. You two need to settle this, as you may not be innocent either. I know World King, and he doesn't carry grudges for no reason.
World King has added you as number 29 (although nameless) on the OU Sign Ups. He said that he will edit your name in when all 32 have signed up.
I apologize for his immaturity. :<