2 Corinthians 11:16-18
2Co 11:16 I am talking again. No one should think I am stupid. But even if you do, accept me as a stupid person, so that I too may brag a little.
2Co 11:17 What I say with this bragging confidence, I am saying not as the Lord would but as a stupid person would.
2Co 11:18 Since many brag according to the flesh, I too will brag.
Paul had been accused of working kata sarka (according to the flesh) and put up quite a defense that his actions were kata pneuma (according to the Spirit). Now, he takes a break from that defense and responds as he says a stupid person would: by bragging. He will go on to count down both his pedigree as a missionary, and his sufferings as evidence of his commitment. Sometimes you have to respind like a stupid person to get through to a stupid person.
It is okay to try to convince people of our sincerity like this, but it should not become a habit. Most of the time, simply walking en pnemati (in the Spirit) and speaking the truth in love is enough.
LORD, give us your wisdom when responding to the accusations of our critics.