Having a sense of power and control over our environments is closely linked to our very senses of survival in the best of times, and certainly becomes more explicitly linked with survival after experiencing trauma.
The vast majority of humans become very primitive, very defensive, and very reactive when we believe our our senses of power and control are threatened (whether or not our true power and control are actually threatened is not the issue, it is the belief that triggers the primitivism).
Unknown Threats Are Scarier Still
As humans, if we are not sure where or what the “threat” is exactly, we tend to overreact to everything that seems even remotely related to the issue.
Think about the immediate and vicious reactions some have to any mention of the word “racism” or “climate change”. Absolute reactivity at the mere mention of the words! Watch what happens in an online comment section when a woman merely types out the word patriarchy and allows it exist in the ether. If it is read by a wide (mixed) audience, it will eventually be attacked. Just by saying certain words people can and do get triggered! Truly. This is not meant to be pejorative. It is what humans do when we feel threatened.
Our modern systems and policies around them are complex, which adds to difficulty in managing our fears and anxieties. It is much easier (and our primitive brains believe it is better) to just shoot down anything we don’t quite understand if we are feeling threatened.
Feeling Threatened Causes Us To Become Irrational And Primitive
It really cannot be overstated: Fear evokes a primordial response in humans. Lessening fears in any way possible by any means possible will always be the first reaction a human has when faced with a confusing and possibly threatening world.
Whether or not we are conscious of or acknowledge the fear is irrelevant. When we are frightened, consciously or (usually) not consciously, we act in ways that serve to protect us in the best ways we know how in the moment at hand. These are often quite primitive and brutal ways when examined objectively. Avoidance and oppression are common reactions.
It actually takes a lot of practice for most of us to not go directly into a reactive survival mode. In survival mode, no humans (none, zed, zero) are focused on fairness, the rights of others, or on long term strategies, we are focused on survival; we get primitive, defensive, crazy even. We also get extremely self absorbed. 
Power and Primitive Acts
Recognizing that worries about power and control often trigger deeply defensive reactions, leads to a highly convincing explanation for why some people become so defensive (to the point of denial and outrage in many cases) when their routine acts of privilege and power are identified and labelled as unacceptable. This also holds true for challenging people’s beliefs about how the world “ought to be”.
Others have noted that when we challenge people’s beliefs about the world, we are actually challenging people’s senses of identity. This is true, and already we can see how that would frighten people.
But challenging people’s beliefs actually goes beyond that. When we challenge oppressive acts or beliefs, we are tearing down people’s perceptions about how the world is and with that, their senses of how to have power and control within the world. This can easily become a terrifying prospect for all people. But especially if and when people are already saddled with outsized anxieties about power and control.
Reacting defensively and/or oppressively does not excuse any acts of oppression at all, but it is simply an attempt to understand more fully how oppressive acts and beliefs arise.