Pure motives as seen in Paul is the exaltation of Christ. Impure motives as seen in these brethren is the enhancement of self. So out of jealously, there were those who were trying to hurt Paul. Instead of lifting him up in prayer, they were tearing him down in prison. But we all know that words can hurt and hurt very deeply.
Nobody likes to be attacked by another.
Nobody likes to be slandered and maligned by others. Paul was no stranger to friends letting him down and tearing him down. When he needed affection he found affliction. These were the things that had happened to Paul. There were the bonds that held him and the brethren that hurt him.