Persecution brings rejoicing because it places in the company of the apostles and prophets. Jesus says that when we are persecuted we are placed in the line-up of the greats. But even better, you will receive a reward for our troubles. You must wait until you get to heaven to receive it, but it is surely there. Furthermore, you should rejoice in persecution because it proves that you are really part of the Kingdom and not an imposter.
Persecution is the badge of authenticity.
So when Jesus' Kingdom encounters the world it experiences persecution for withstanding the world's goals and values. But rather than causing despair, this brings about rejoicing in the Kingdom. The world also is affected by the conflict with Jesus' Kingdom. Jesus' followers have the effect of salt and light in the world. It is difficult today to grasp the full impact of the salt metaphor.