Friendship circles are a two edged sword. Friendship builds relations of warmth and intimacy, encourages community and builds a sense of self worth. All good. But friendship can easily exclude. I can't be friends with everyone, and to maintain friendships I spend time with friends more than strangers for our friends, and in conflict take their side rather than the side of a stranger. Friends can make me feel included, but by definition can make others feel excluded. So I can reinforce and strengthen my sense of belonging by excluding others from my friendship circle. But not always of course, and probably rarely consciously. Most of the time I like spending time with my friends: I see them, I go over and talk to them missing the 'other' I walk past to get to the friend. This happens in any group meeting. The meeting closes and we congregate to those we know and enjoy.
I can't think of anywhere in the Gospels where Jesus says we should be friends. He says that he calls us friends and that we should mimic his love for us by loving one another. (John 15:12-17) Our love for one another is found in our unity with Christ. Indeed, the passage just cited follows that great teaching on the vine and its branches where Jesus commands us to abide in him. (See especially John 15:1-11)
Elsewhere Jesus tells us to love our enemies. (Matt 5:43-48) Imagine if your enemy attended the same church as you! What a great opportunity to obey Jesus' command to love as he loved us (see Rom 5:6-11) And what a better picture of the kingdom such a church would be than a church of friends. It would of course be harder work at times, and there would be times when we would prefer the company of our friends at church. But a church that has enemies within it would be a great place to practice one's discipleship.