Did Lemech really copy the deviant practices of his generation?
(4,19) “And Lemech took for himself two wives; the name of one was Adah, and the name of the other was Tsilah.”
Rashi explains that it was the custom of the generation of the flood to take two wives - one for producing children and the other for the pleasure of marital relations, and this second one would be given a potion to make her sterile. The wife of Lemech whom he took for producing children was called Adah because this name connotes that she was despicable to him and removed from him. And the wife who he took for pleasure was called Tsilah which connotes that she always dwelled in his shadow.
But the obvious question here is that a later posuk says that “Tsilah also gave birth”! The Re’eim answers this problem by explaining that the contraceptive potion did not always work, and so she also gave birth despite having drunk the potion. But even with this answer we are still left with the problem that Chazal teach that Lemech was not a wicked person, and therefore how could it be that he copied the abominations of his generation?
Therefore it seems to me that Chazal mean to explain that Lemech also took two wives like the custom of his generation so that they would not quarrel with him. and in addition he called them names which suggested that he was keeping their practices. Thus he named one of them Tsilah as if he had given her the potion which makes women barren, but in fact he never gave her, and therefore the posuk teaches that “Tsilah also gave birth” because she had never drunk the potion. But the people of his generation could not fault him for this since the potion does not work for everyone, as the Re’eim explained.