At a loss in the Midwest...

How would you tell a "friend" that you think their child has SPD? Or at least suggest they look into it? This person's relatives have already suggested that they think her child has autism & that was very offensive to them. Our children are playmates despite the many years of our children being verbally & physically hurt by their child. In the past, we tried to confront lovingly (solely from a behavioral stand point) but the parents always over-reacted (both toward us & how they tried to solve the issues with their child). It was more like defensiveness toward us, yet punishment to their child to show us they were doing something about it, but almost to make us feel guilty. I just don't know if they would hear it from us. Thanks.