The enemies of Paul in Corinth waged war with carnal weapons. They boasted in the flesh of things which actually presented them as foolish. Yet, the Corinthians put up with their folly, and were being deceived by their false doctrine (11:3-4). In order to shock the Corinthians back to normalcy, Paul stooped to reluctant boasting. He engaged in this to make a point, and his boasting is laced with irony as he emphasized his weaknesses (11:22-33).
These false apostles praised themselves as being great and powerful. Ironically, their demeanor represented a characteristic foreign to Christ (v. 17). Thus, Paul emphasized his boasting as reluctant. It was for the purpose of showing the folly of those who claimed to be apostles, but were not. The Corinthians tolerance of these boastful men was thought to be wise. However, these boastful men were fools, as were the Corinthians for putting up with them (v. 19).
The folly of the Corinthian’s tolerance is exposed in the stark contrast of their treatment received from the false teachers, and from Paul. The deceivers reigned in their midst as despots, consumed their possessions as they took advantage of them, towered above them in self-exaltation, and even abused them with violent words and actions (v. 20). This they did while tearing Paul down in front of them. Paul paradoxically suggests that his refusal to treat the Corinthians as such was due to weakness (v. 21). He loved them, and expressed that love in the humility of service (cf. Matthew 20:26-28). He would go on to elaborate in pointed, reluctant boasting of his accomplishments in Christ (11:22-33).