The Torah commands us not to take bribery because “Hashochad Ye’aver einiey Tzaddikim…” loosely translated, the “bribery will blind the eyes of the righteous etc…”.
The Torah does not tell us that bribery can cause impaired judgment; rather that it “will” cause impaired judgment. The Torah is stating a fact, a rule of nature, bribery affects the recipient to the point that he is not capable of rendering a bias free decision.
Chazal tell us that a judge is forbidden from taking bribery even from the one whom he thinks is innocent and he was either way going to rule in his favor.
“Shochad” is a fact and rule of nature just like any other other rule of nature. Just like there is a rule of nature that gravity is a force that pulls down- there is a rule of nature that bribery impairs objective thinking and decisions making. This cannot be overcome by anyone, regardless of how great they are, because this is a law of nature- It is how Hashem created the world.
Rav Dessler (Michtav Meliyahu vol.1) applies this concept on a very personal level. We all have our inner wants and desires, the pleasure we seek and wish we had. To a certain degree we are all bias and “Bribed” by our lusts and desires. When we have to make a moral or ethical decision, lingering in the background is our desire for, pleasure, lusts, honor etc.,- all this bribes us in a certain direction.
This being the case how can we possibly make a rational and objective decision when faced with a nesayon?
To this Rav Dessler answers that Hashem gave us the power to overcome our personal biases (As long as there is no outside bias/Bribery) and make a true rational decision when we are faced with a nesayon. But this is no easy task, and one has to really be seeking the truth to achieve this clarity of sight and true honesty.
We have to think about things, and re-think them and then be completely honest with ourselves.