‘For his letters, they say, are weighty and strong, but his bodily presence is weak, and his speech of no account.'
Using letters to exert his authority would indeed only serve to justify the words of his opponents who accuse him of being able to issue powerful written edicts, but when present among them, of being weak and a deliverer of ‘no account' words, the raging lion turning out to be a mouse. So he will certainly not do that.
The Corinthians had undoubtedly shown Paul's severe letter to the newcomers. And this had been their contemptuous reply as they supported each other's authority, ‘Weighty and strong when absent. Weak and unimpressive when present.' They were well aware of Paul's physical weaknesses and sought to use them as an instrument with which to degrade him. This is a question that Paul will deal with later (2 Corinthians 12:7-10).