“To be fair” is to use the same measure when you weigh for yourself, your loved ones, those you dislike, and even your enemies. This applies to physical things as well as ideas and spiritual matters. Indeed, this can be a very challenging task.

Allow me to give an example.
When Oxford decided to honour Truman, the Oxford graduate and Cambridge Professor G. E. M. Anscombe wrote to oppose such a decision. The following excerpts are from her privately printed pamphlet titled “Mr Truman’s Degree”.

“In 1939, on the outbreak of war, the President of the United States asked for assurances from the belligerent nations that civil populations would not be attacked.
In 1945, when the Japanese enemy was known by him to have made two attempts toward a negotiated peace, the President of the United States gave the order for dropping an atom bomb on a Japanese city; three days later a second bomb, of a different type, was dropped on another city. No ultimatum was delivered before the second bomb was dropped.
“

and

“It was the insistence on unconditional surrender that was the root of all evil. The connection between such a demand and the need to use the most ferocious methods of warfare will be obvious. And in itself the proposal of an unlimited objective in war is stupid and barbarous.
“

and

“Protests by people who have not power are a waste of time. I was not seizing an opportunity to make a “gesture of protest” at atomic bombs; I vehemently object to our action in offering Mr. Truman honours, because one can share in the guilt of a bad action by praise and flattery, as also by defending it. When I puzzle myself over the attitude of the Vice-Chancellor and the Hebdomadal Council, I look round to see if any explanation is available why so many Oxford people should be willing to flatter such a man.
“

Anscombe was fair.
Truman stated that the atom bomb will be dropped only on military targets, yet it was dropped on heavily populated civilian areas of very little military significance.
Truman was unfair. He was a war criminal.
We had worse than Truman, but that’s another story.