At the beginning of Chapter 15, John the Savage is pushing through all the Deltas. He does not really pay any attention to them. The reason for this is the fact that his mother has just died. So he has his mind only on his grief. As Huxley puts it
his mind was elsewhere–with death, with his grief, and his remorse; mechanicaly, without consciousness of what he was doing, he began to shoulder his way through the crowd.
All of the Deltas get a bit annoyed at John as he does this. They all sort of scold him, asking him what he thinks he is doing, who he thinks he is pushing.
Later on, when he needs the Deltas to stop misbehaving, the Sub-Bursar tells them that he will stop giving out the soma if they don't shape up.