פירוש על עבודה זרה 33:6

This final section discusses a fascinating contradiction between Ulla’s actions and his preaching. On the one hand, in reality he would kiss his sister, either on the hand or on the breast (I assume this was considered normal social behavior in the time). This is his sister after all. On the other hand, he also preached that a man should stay away from even getting near any woman, just as we tell a nazirite to stay away from the vineyard.
Interestingly, there is no resolution to this contradiction.