me_irl

No, the point is that the saying implies that considerable or extreme anger is a thing that emerges from behind a mask of politeness, it implies anger is more authentic.

The conceit is that this phrase is almost never used when someone displays considerable to extreme happiness or sadness.

The phrase is used mostly as a flippant way of dismissing displays of anger, but that it is almost never used to dismiss anything else, implies that people can mostly only be angrier, truly/authentically, than they generally act as.

That's the manupulation inherent in the usage of the term.

You've just tried to recontextualize and thus slightly redefine the term and how it is used, such that it avoids the problems of how the phrase is actually used.

Are you going to tell me that when someone hears good news, and becomes jubilant, or hears tragic news, and breaks down into tears... other people often remark that they're 'showing their true colors'?