What does this mean Man usually avoids attributing cleverness to somebody else unless it is an enemy by Albert Einstein. Anyone have some input?

Attributing cleverness to one's enemy makes him a great adversary. That way, if you suffer defeat by your enemy, even on a small level, it does not make you look bad, since you have made it known that he is very clever, etc. Conversely, if you defeat your enemy, you look much greater than if you had defeated anyone else, because you have triumphed over a very clever and capable foe.