He's obsessed with this woman because she is everything he cannot be: Kind, considerate, open minded, generous, true to her creed, loving, undogmatic (mostly ), intelligent, brave, and sweet. She has set a standard so far beyond the imbecile's reach that he must necessarily live and die in failure. Is it any wonder he does not like her?
I do not agree with her down the line, but I admire her, and I'll admit that in several ways, she's better than me. He could never do this.