Yet in the paragraphs before that you are speaking about how facebook _is_ changing the world.
Apart from that minor (mistake?) thing, I do agree with you fully. Using facebook is a good way to surround yourself with people who think and do exactly as you do, which is not beneficial.
Same goes for other types of social media, but you can break it easier with for example twitter. You can follow people with different ideas than yourself and be challenged by their view, which is a healthy thing to do. I feel like the treshold to that is lower on twitter than on facebook. But then again, I am not a facebook user myself since a couple of years ago, and that experience might have changed.
Though on the flipside, it can also be used for good. Not because you are into some kind of weird belief that will be reinforced by others, but for example imagine that you want to learn esperanto, there might be facebook groups full of people doing the same and it might help you learn it with greater ease.