Changing others begins by changing yourself first
he seems like an insensitive person to leave you with HIS workmates at his company picnic. I would be upset too if that happened to me. But keep in mind that he must have had a reason for doing so although it is insensitive to your feelings. After you find out, If you find out why he did so. I just might temper your anger that you feel. Your marriage has probably endured much more than that issue. In time you will both get over it and will be able to put it in perspective. Hopefully he won't do that kind of thing again.