The Internet is probably just an acceleration of something that has been happening for the past few centuries. Not so long ago, you lived in a small village all your life. Travelling to the next village over was a long and dangerous affair. Travelling to the closest city was almost unthinkable. Travelling to another country was a one-way trip to only be done as a last resort (i.e. your country was kicking you out). The only people who you ever interacted with were the people in your village and they likely all shared the same beliefs.
As transportation improved, people could travel quicker. Whereas you might get 20 - 30 miles a day by travelling on horseback (perhaps less if you were carrying anything), the railroads or boats could go much faster. Nowadays, cars can cover "one horse travel day" in under an hour. Planes can go even faster than that. As the speed and safety of travel improved, more people were able to interact with more people who lived further from them. Things that would have been unthinkable in the past - visiting a country hundreds of miles away for a week for fun - were now possible. This meant more interaction with even more people.
Then television allowed people to "virtually" expand their travel horizons. You could see how people in Japan lived by watching a show about Japan on the TV instead of actually travelling there. The Internet expands it even more because now you can both look up information AND talk to someone from that location. It essentially turns the entire world into a village.
So, yes, the Internet might be responsible for a few long-held beliefs disappearing. However, it's not unique to the Internet. The Internet is just the latest in a long line of advances which have been chipping away at these over the past century or two.