The NT said it correctly - NTs only want others to acknowledge their positive emotions - because negative emotions = weakness, and in NT society weakness is invariably a perjorative term. Now, in my Aspieness I would never equate being upset to being 'weak', and neither would I stigmatize any and all weakness. Isn't it just human to feel upset? What's wrong with not being strong?
NTs have this innate Japanese countenance (no offense to the Japanese); be strong, and be the same as everyone else. It's not even a sign of these hard-nosed egocentric times; my grandmother used to say to me "Chin up!" and "Never let anyone see you cry!"; sentiments echoed by family members, teachers and peers alike. I never understood why, even now I still can't get my head round it. I can understand the need to keep negative, often counterproductive emotions such rage or hostility in check, but to be upset? That to me is a whole different ball game. To NTs however, all such negative emotions are grouped together. You have to be unfalteringly strong and thick skinned, otherwise you won't belong to the group..(which paradoxically in itself is weak; not having the courage to simply be yourself and acknowledge your life as a human not a damn robot).