It is stated in Medrash Hagadol:
“And Yitzchok loved Esav: Didn’t he know about Esav’s degraded, corrupt conduct? The pasuk says (Tehillim 139:21) that one should hate those who hate Hashem. So why did he love him? Rather, he only loved him outwardly in order to draw him close. He made a kal v’chomer that if he acted so badly when his father loved him, he would act even worse if his father hated him. And our sages tell us (Sotah 47A ) that one should always draw close with the right hand and push away with the left.”