It’s almost obvious that both sympathy and antipathy, once they influence decisions and choices, are disadvantageous in leadership situations.
Sympathy and antipathy are conditioned, emotional states. Sympathy maybe evoked by weakness and antipathy by strength. They maybe based on temporary perceptions, opinions, etc. and once conditions change sympathy may become antipathy, and vice versa.
The same applies to situations that may evoke emotional reactions, like fear and excitement for example.
Some managers intuitively know this, and they try to stay neutral, which is laudable; to accomplish neutrality they focus their attention on skills and talents and neutralize sympathy or antipathy, as well as likes and dislikes by evaluating people and situations based on how they may or may not contribute to the outcome of projects. This may do on a management level.
On a leadership level detachment and neutrality is achieved by keeping awareness focused on the context: the principle based concept for the organization (it is important to note the corollary: without a principle based concept, no leadership exists in the organization). The more essential the concept, the more it enables organic organization, i.e. enabling the emergence of hierarchies, whereby skills and talent (on the plane of rationality) are appropriately subordinated to the intellect and it’s corresponding style elements: detachment, self-control, intellectual intensity, etc..
A leader’s value is determined based on to what degree they are aligned to this concept which in turn enables them to fearlessly do what needs to be done.