[Terretta]

> Matt needs to calm down ...

... means, "this seems more important to Matt than it does to me" and "he should just accept it shouldn't matter to him any more than it does to me".

Which, when paraphrased, explains why the comment tends to further provoke those who are passionate about something dear to them.

Often it's dear, and they are uncalm, because it came from them or is part of them in some way. That's the anti-calm appealed to by "think of the children", an inciting phrase. We're to recognize that our creations are worth our care.

Put another way: not all indignation is unrighteous.