NEW : Sheriff John Arpaio suggests Justice Department investigation is politically motivated . Justice Department investigation details slurs and language used against Hispanics . Feds probe how sheriff 's office handled 432 cases of sexual assault and child molestation . Assistant attorney general say sheriff 's office failed to cooperate in the probe .
NEW : Sheriff Joe Arpaio suggests Justice Department probe is politically motivated . Justice Department letter details slurs and profanities used against Hispanics . Feds probe how sheriff 's office handled 432 cases of sexual assault and child molestation . Assistant attorney general say sheriff 's office failed to cooperate in the probe .