Quite big fuzz with a lot of exaggeration and a lot of unnecessary and not to verify statements, like
my friends noticed FEAR in their eyes - they were trying to hide their carry-ons, and were SCARED that they might be the next to be refused to fly if they didn't check in their valuables
I understand you are upset but wouldn't have weighing and measuring your carry-on resolved the whole problem. If you reacted at the gate the same way you wrote your post here I somehow can understand the flight manager’s reaction.