I have a friend (non-JW) who's fallen for a girl who's no good. She's very pretty, but has been coddled since she was an infant. The girl is 25 years old and her mother still does all of her laundry, pays for her credit card, and comes over to clean her apartment periodically. Growing up she surrounded herself with friends who would do whatever she said, mostly unattractive girls who wanted to hang out with a "hot chick" and unattractive boys who were just happy she'd even talk to them.
She teased my friend into thinking that she was really interested in him. He initially didn't want to have anything to do with her because he knew her personality, but he was lonely and eventually gave her an in. He fell for her and after some time, he asked her out. Much to our surprise, she rejected him. We couldn't believe it since she had told him to his face that she had a crush on him. Undeterred, he kept on hanging out with her, spending lots of money on her, and now he's at the point where she completely dominates him.
He does whatever she wants and spends however much money on her as she wants, and they're not even a couple. She lets him kiss her, but she won't have sex with him. At this point he's a sad, madly-in-love fool, and she's a complete manipulative bitch. A few weeks back we went to a fancy event. He bought her ticket. At this event, she yelled at him in public and told him to back off because he was moving too quick. She didn't want people to think they were a couple. He disappeared and we found him an hour later crying. The next day he pretended nothing had happened. He refused to admit what happened and attributed the whole mess to his mixing alcohol with antibiotics.
The moral of the story is that, regardless of what we try to do, we can't get through to him. He's madly in love and desperately wants to be with this girl, even though he knows she treats him like crap. When we try to reason with him, he finds dumb ways of rationalizing her behavior. This is how it is with a devoted JW.
They've fallen in love with the concept of having the truth and living forever in a paradise Earth, the belief that we are now living in the most important period in the history of mankind and we have been fortunate enough to have been given a front row ticket to history in the making. To reason with a JW is like trying to reason with my friend. It's impossible. He won't come to his senses until he becomes disillusioned with her, until his she hurts him one too many times. At that point, it'll be crystal clear to him and he'll feel like an idiot for having made such an ass out of himself. The same's true with JWs. They have to become disillusioned with the Watchtower before they're able to reason. Once they've fallen out of love with Watchtowerism, then, and only then, is it possible to reason with them.