If someone caused distress, I'm not the one really affected. To some extent--although I don't want to emphasize this too much--it has affected all of you.
The majority of you have imposed a severe enough punishment on that person.
So now forgive and comfort him. Such distress could overwhelm someone like that if he's not forgiven and comforted.
That is why I urge you to assure him that you love him.
I had also written to you to test you. I wanted to see if you would be obedient in every way.
If you forgive someone, so do I. Indeed, what I have forgiven, if I have forgiven anything, I did in the presence of Christ for your benefit.
I don't want Satan to outwit us. After all, we are not ignorant about Satan's scheming.