The yetzer hara can LEAD to an aveira. It is not an aveira. Hashem created us with two yitzros, as we can see by the creation of Odom, where “VaYitzer” is written with two Yuds, as opposed to when animals were created and the same word is written with only one Yud. This teaches us that animals have only one will or instinct or yetzer that Hashem gave them. Human beings have two, and this results in the ability to differentiate between right and wrong. It is our choice to follow one yetzer or the other.