Love enters this discussion because Agape, the Greek word for "Love", is a quintessential part of the Law of Thelema. In fact, Thelema and Agape both evaluate to 93 when computed against the Greek Gematria. That these concepts are tightly bound and intertwined is a vital concept to comprehend in the attempt to incorporate the Law of Thelema into one's Life.
Love is not a particularly complicated subject, but it is a deeply important one to the follower of the Law of Thelema.
In essence, Love is here very nearly a synonym for the word "respect". If you love your neighbor, then you respect your neighbor, and everything they stand for. You will, therefore, be inclined to show them respect, and thus, create no unneccessary conflict with them in Life.
I interpret the inclusion of Agape in the Law of Thelema as this: While we are each to exert our Will (Thelema) in our Life, it is to be tempered by Love (Agape). If an action we are about to take, seemingly due to our Will to accomplish the task, fails to exhibit Love -- respect -- for another star, then perhaps it is time to review the action to ensure it really fits our True Will. Love is the law, love under will. There should never be any conflict between the two components if we are truly on the right Path.
Books You Might Enjoy:
John Musick - The Witch Of Salem
Julius Evola - Against The Neopagans
Roger Bacon - The Mirror Of Alchemy
Morwyn - The Golden Dawn
Arlo Bates - The Pagans