A story of forgiveness

PS-click on the pic below it is a great face when seen close up

I have a story of forgiveness which I think is one of the hardest and most valuable lessons we can learn as humans. My oldest son has had a good friend the last couple of years that he has suddenly not got along with this year, he calls him an "enemy". The situation is even trickier because I am friends with the child's mom-she is such a sweet person AND related to my bestest friend. Anyway we all plan a camping trip for August with us and kids and I don't think another thing about it. So "A" comes in after school sobbing and when I ask him why he says this other child called him a "retard" twice. Now my friends, being a special education teacher-nothing infuriates me more than that word. Being a mom and hearing it is just about as bad. I immediately call the teacher, we discuss and I feel better, and older son is let off the hook for camping-he is frantic about having to go with this child.
So son comes home on Monday and says "We all moved seats, guess who I HAVE to sit by", yup you guessed it. The teacher has a conversation with him about how this child feels and how he has been picked on and maybe there is a way "A" can teach him to be a friend.
Soooo Wed, oldest son comes bounding through the door telling me he is inviting a friend for a sleep over (yeah you know what is coming). The same "enemy" because this is their "grand opening" as friends again (his words).
What do I say??? Yes of course...Forgiveness can be learned at any age...