Anger And Status

One of the preferred methods of convincing a person that they don't have real personal power is to challenge, oppose, and invalidate their anger. If a target expresses anger, even if the reason for the anger is obviously valid to everyone, they will be treated as if they are acting "out of line", or "silly", "whiny", "crazy", or "negative".
The purpose of this belittling is to display "higher status", and to "knock them down a notch".

Expressing anger openly and freely is a privilege that is only afforded to those of higher rank in a primate group, and is seen as a freedom of status. Anger expression is USED as a POWER DISPLAY by both status-displaying primates and status-seeking humans (think "display" as in Silverback Gorillas beating their chests).

SO when a person who is NOT a status-monger expresses anger GENUINELY who does NOT use it as a social power and status display, they won't know WHY they are being treated with disrespect and condescension. It doesn't make sense, because it's completely out of context. Further, their confusion feeds the status-seekers, who will often go further and further with their belittling and invalidating behaviors.

In other words, when status-seeking humans display anger and hostility, they aren't actually just doing it because they are ANGRY. They are doing it as a Power Display. They learned a long time ago to use a display of "anger" as a way to try to display how "powerful" they are.
When NON-status seeking humans display anger, they are actually ANGRY about something that really happened, they aren't playing at a power and status display.
BUT~ any status-seekers who are within EARSHOT of a non-status-seeker's expression of anger will RESPOND AS IF there is a "game" afoot. They hear the "anger display" not as an actual expression of emotion or frustration, but as a CHALLENGE, and they will try to DOMINATE the other person as if that's what THEY are doing.

~Much like a Silverback Gorilla would probably think you were challenging him for his status position if you frantically swatted a swarm of flies that landed on your shirt. You aren't actually challenging him, but that's what it looks like to him, because that's what HE does. He doesn't THINK about what you're doing or not doing, he just responds to his assumption. Humans have similar compulsive reactions to rank-challenges, whether they're real or not. 

Unlike Gorillas, humans try to pretend they don't create and maintain social hierarchies like the other Great Apes. Humans want to believe they are above that sort of thing, but this base, non-intellectual, counter-productive behavior is evident to those who know what it looks like in groups of humans everywhere.