YOU SAID:
Are you seriously this stupid?
INTO JAPANESE
本気でそんなバカなの?
BACK INTO ENGLISH
Are you really that stupid?
INTO JAPANESE
そんなにバカなの?
BACK INTO ENGLISH
Are you that stupid?
INTO JAPANESE
そんなバカなの?
BACK INTO ENGLISH
Are you that stupid?
That didn't even make that much sense in English.