Do what thou wilt shall be the whole of the Law.
Yes. He wanted people to sacrifice a male child of above average intelligence. The book, as I recall was Magick in Theory in Practice, but I may be wrong. EDIT- Yeap. I was right, MiTP, relating to the highest spiritual ideals.
The problem is, is in the understanding of those words. Crowley was VERY pro-life; so pro-life that he viewed the sperm from a man as life. When he is suggesting that, he is actually calling for the use of male ejaculate, generally by masturbation. Crowley was a fan of hiding what he was trying to say in arcanums, and this is just another one of them. Remember, he grew in very strange times for morality.
He was neither a Wiccan [Indeed Wicca is possibly an off shoot of Thelema] or a Satanist [Being founded years after his death]. He was a Thelemite, like myself.
If you have any questions, feel free to message me.
EDIT: Here is the full quote for you: "For the highest spiritual working one must accordingly choose that victim which contains the greatest and purest force. A male child of perfect innocence and high intelligence is the most satisfactory and suitable victim."
There is also a note, "‘It is the sacrifice of oneself spiritually. And the intelligence and innocence of that male child are the perfect understanding of the Magician, his one aim, without lust of result. And male he must be, because what he sacrifices is not the material blood, but his creative power."
Love is the law, love under will.