In "Prayer For My Daughter," W.B. Yeats considers what he really wants for his daughter, who at the time of his writing, is yet an infant. He wants her to grow to be beautiful--and what father doesn't?--but not so beautiful that men love her for the wrong reasons or that she believes beauty to be enough. He wants her to be "chiefly learned"; that is, more educated and intelligent than beautiful, because "Hearts are not had as a gift but hearts are earned," meaning that a true lover loves the mind, the personality, and these things must be nurtured by education.
He adds that "to be choked with hate / May well be of all evil chances chief," meaning that hatred destroys beauty of any kind. This is where he gets to the "intellectual hatred":
An intellectual hatred is the worst,
So let her think opinions are accursed.
Have I not seen the loveliest woman born
Out of the mouth of Plenty’s horn,
Because of her opinionated mind
Barter that horn and every good
By quiet natures understood
For an old bellows full of angry wind?
He means that thinking oneself smarter than others, holding her opinion to be the best, and arguing for it, is the worst sort of hatred, the most unbearable. He says even the most beautiful and gifted woman, born with every grace, can become--because of her "intellectual hatred"--"an old bellows full of angry wind."