Even though you (Brahma) are the most powerful being, this act (Brahma was sexually inclined to his own daughter) does not suit you because your character is followed for spiritual improvement by people in general
SB Canto 3
Even though you are the most powerful being, this act does not suit you because your character is followed for spiritual improvement by people in general.
It is said that a supremely powerful living entity can do anything and everything he likes and such acts do not affect him in any way. For example, the sun, the most powerful fiery planet in the universe, can evaporate water from anywhere and still remain as powerful. The sun evaporates water from filthy places and yet is not infected with the quality of the filth. Similarly, Brahmā remains unimpeachable in all conditions. But still, since he is the spiritual master of all living entities, his behavior and character should be so ideal that people will follow such sublime behavior and derive the highest spiritual benefit. Therefore, he should not have acted as he did.