Fire Main's 3rd standard attack isn't the only one that can ignore "Taunt". Lightning Mains's 1st standard also does this.

It's another one of those "poor skill desc
riptions" that for some reason still exist. That "defensive skills of the opponent" is actually referring to the "Taunt" skill that is the 2nd effect of Hinata's mystery, the 1st being the high evasion. Any Ninja on the front that has Taunt will be the sole target of enemy standrad attacks EXCEPT the special standard attacks already mentioned and attacks like Fire Main's 3rd standard and Lightning Main's 1st.