Why? Because here's an amazing thing about people, both men and women: people tend to conform to what we expect of them.

Let me be clear.

People tend to conform to what we expect of them.

For instance, let's say you get a new job and your new boss immediately assumes you're a dick. He talks down to you, rolls his eyes at you, and acts as if your mere presence is an insult to everything he stands for.

How would you end up behaving towards him? That's right you'd start acting like a dick. He treats you badly because he expects you to be a dick. And you start acting like a dick because he's treating you badly.

The same is true with women and dating. If you meet and date women believing fucked up stuff about them, you will only encourage that fucked up behavior. If you never trust the woman you're with and are always jealous, then you're just going to encourage her to do things behind your back. After all, she's going to get yelled at by you anyway, so she decides to start withholding information.

In the therapeutic world, this is often referred to as "enabling" : when our shitty behavior encourages the people around us to adopt shitty behavior.