I understand, have this problem also very difficult to manage, my son just says what's on his mind which is usually very blunt. This can cause a lot of tension in the house but just have to keep reinforcing and trying to get him to understand that what he says is upsetting.
Anyone that make a negative comment to him or what he perceives as negative he gets very upset at times can lead to meltdowns.
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A mother/person looking for understanding!