That's not what a broker does. A broker is basically in sales. He takes company research done by analysts and tries to sell you company financial products. He doesn't care which direction you go as long as you do something so he can take his commission, and a little extra if you are buying a company product he might be trying to push.

A market maker is the guy who's tying to capture the spread, but they don't really go around trying to get the public to buy and sell.