It has long fascinated me how easily love can give way to a powerful counter-emotion, like jealousy, hate, rage, etc.  You know: how parents who love their child one day can, the next, boot him out of the house and into homelessness and uncertainity just because they discover that he (or, indeed, she) is LGBT. What makes people do that? Kill the thing they love? (Oscar Wilde: Ballad of Reading Goal)

It obviously fascinated Shakespear too, this human tendency/weakness, since he made it the subject of his tragedies, like Othello.

I guess we'll never know fully the answer to that one.