You requested an open discussion, correct? That means you have to open to opposing opinions at the same level we do. Is that something we can agree on?
Have you ever seen somebody cry at a wedding? A wedding is a happy thing so if somebody is crying at such an event they must be lying, right?
Have you ever seen people laugh at a funeral? If they are laughing they must not be sad, right? Of course not! Maybe they are recalling a fond memory, maybe they choose to celebrate the life of the deceased and mourn at a later date.
Have you ever been so scared to death (like say you were about to jump out of a plane) that you just started laughing like a lunatic?
Not everybody reacts the same way. There is not a standardized list of how one is supposed to react when facing a deeply moving, upsetting or happy situation. You have the right to choose how you react but you do not have the right to dictate how another person should (none of us do, I am not finger pointing at you). And when they don't react how YOU want it doesn't mean they are lying.