Like a lot of things in life, the thing that makes something so great, is also the biggest drawback. In this case, the danger is the like-mindedness itself.
When you surround yourself with only like-minded people, it’s very easy to stop there and just surround yourself with people who agree with you because you all have the same beliefs, think the same way and do the same things. It becomes very easy to simply accept that something is true because enough of the people around you say it’s true and accept that what you believe is right just because people around you say it’s right.