Regardless of "what" it is... When someone, especially someone we care about, does the "wrong" thing in the moment? It hurts x10. In addition to the "wrong" thing, it also adds in elements of betrayal, misunderstanding, not feeling cared for, invalidation, et cetera.
Personally, I like it when someone laughs at me when I start to freak out. It's not a universally bad/wrong reaction. In fact, I'm not sure there is a universally bad/wrong reaction to someone in a state. Different things work best & worst for different people. Regardless of what the knee-jerk moment is, though... When it's the wrong one for us? Individually? Um. Yeah. Already in a state. That is about to get much worse. Gah! So, so, so frustrating.
Most people, in my experience, are unwilling or unable to change their knee-jerk reactions to emotional crisis. Some people laugh, others mirror, others get angry, others go cold, others get all ooey gooey, others get calm, others, others, others, others. It is worth it, though, to talk with them when I'm not all messed up. Because while their knee-jerk reaction may be set in stone, that reaction may also simply be their set reaction when they don't know what to do. Either way, I gain some knowledge. Either this person helps or makes things worse when I'm a mess. Regardless of how much they intend to be helping or hurting.