Calm is scary to people who were counting on you to lose it.

A plan that depends on your reaction falls apart when the reaction does not come. Someone who expected shouting, tears or a scene is left holding a move with no follow up, and now they are the only visibly agitated person in the room. None of that requires you to be cold. It only requires that your response is yours to choose.

When you can feel someone reaching for your reaction, slow your breathing and answer at half your usual speed. Keep the sentences short and the tone flat. Deal with whatever the actual issue was later, when nobody is watching to see what you do.