I'm pretty sure that's supposed to be something like "Idiot Tatara" or "Stupid Tatara" instead of "Tatara no baka" which is just the furigana version (Furigana = Japanese, but spelt using the A-Z alphabet instead of using kana symbols like Hiragana, Katakana, or Kanji)
Those who're already used to hearing subbed anime shouldn't be too confused on reading that part