You have identified the dark, sticky intersection where epistemology (the study of knowledge) meets incentives and human nature.

When people have knowledge but don't use it—or when their knowledge "mysteriously disappears" depending on whose bread is being buttered—we are dealing with a phenomenon known as rational ignorance, strategic ignorance, or epistemic corruption.

The explanation for this hypocrisy breaks down into a few clear psychological and structural reasons.

1. The Cost of Acting on Knowledge

Acting on knowledge requires effort, risk, and sacrifice, whereas ignoring it is free.

• When it's your bread: If you possess knowledge that can benefit you, the payout is immediate. The incentive structure aligns perfectly with your survival or comfort, so your brain effortlessly retrieves and applies that knowledge.
• When it's someone else's bread: If applying your knowledge only benefits others, but requires your time, money, or social status, your brain performs an unconscious cost-benefit analysis. If the personal cost outweighs the personal benefit, human psychology is incredibly adept at inventing excuses, generating "doubt," or pretending the knowledge doesn't exist.

2. Strategic Ignorance (The "Willful Blindness" Loophole)

Sometimes, people actively choose not to know, or pretend not to know, because knowledge creates moral accountability.

• If a garment company knows a factory is using exploitative labor, they are morally complicit. If they intentionally don't audit the factory, they can claim "we didn't know" when things go wrong.
• This is exactly what you mean by knowledge disappearing when others have the bread. If recognizing someone else’s rights or needs forces a person to give up their own privileges, their brain will actively repress that knowledge to protect their self-interest without feeling like a "bad person."

3. "Where You Stand Depends on Where You Sit" (Miles’s Law)

This is the ultimate rule of institutional hypocrisy. A person's perspective on truth is heavily dictated by their bureaucratic or financial position.

• When a politician is in the opposition party, they have a flawless, hyper-detailed knowledge of how government waste happens and why the national debt is a crisis.
• The moment they win the election and take power, that knowledge magically evaporates. Suddenly, the system is "complex," spending is "necessary," and the nuances change. Their cognitive apparatus hasn't decayed; their incentive structure has flipped. They knew which side their bread was buttered when criticizing, and they know it now while governing.

4. Group Identity Over Objective Truth

Humans are social animals before they are rational animals. Often, the survival of our "tribe" (our political party, our company, our family) is more important to us than objective facts.

• If a piece of knowledge benefits an enemy group or a rival, people will actively suppress it, mock it, or label it as fake news.
• They will ruthlessly apply logic to defend their own group's mistakes while using that same logic to tear down others. The knowledge is weaponized when convenient and buried when it threatens the home team.

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As David Deutsch would argue, this hypocrisy is a failure of moral progress. Moral knowledge—the understanding of how to treat other people as ends in themselves rather than tools—is just as real as scientific knowledge. But just like our ancestors and the fire, we often choose to sit in the cold because changing our ways requires a creative effort we are too comfortable to make.

We can take this thought experiment further if you'd like. Would you want to look at:

• ** Upton Sinclair’s famous critique** on this topic ("It is difficult to get a man to understand something, when his salary depends upon his not understanding it").
• How we can design systems or institutions that force people to apply knowledge fairly, regardless of whose bread is buttered.
• Historical examples of "strategic ignorance" in corporate or political scandals.