Suwako is of the Vile race is a reference to Mishaguji.
Mishaguji in Touhou are powerful curse gods who Suwako brought under heel in Touhou lore. They still act as her servants to this day.
Mishaguji in SMT are a recurring demon that always belongs to the Vile race. It's had several designs over the years but one recurring element to it's design is that it looked rather... phallic... Apparently their most prominent godly domain was fertility and making sex better, a trait which is conspicuously absent from their Touhou incarnations.
