I guess I would need to know more about his behavior. Is the "shut your mouth" example typical, with excursions into worse behavior? Where I'm heading is, this may be more than just feeling emotions intensely. It may be a problem with behavioral control that needs to be addressed.
With regard to the other parents -- is your son regularly exploding at their children and verbally attacking them? If so, this may actually be their attempt to build bridges to you. It may be that they are trying very hard not to brand you as Evil Parent of Evil Kid and instead are trying to start a dialog with you about it.
