If the phrase "An emotional moment" refers to the heartwarming atmosphere, which expression can I use if I want to express "rage" or "disappointment" among people in the opposite circumstances?
Good question! "An emotional moment" can actually be used to refer to either positive or negative emotions. So here if it describes the heartwarming atmosphere, it can also be used to describe an environment of sadness or anger. There are other ways you could possibly describe these potential negative responses as well, such as by saying "a disappointing moment" or "a disheartening moment". However, the expression "an emotional moment" can express a negative nuance just as much as a positive one.