physical chemistry - Destabilization of antibonding MO vs stabilization of bonding MO

My textbook writes that

The net energy stabilization due to the occupation of a bonding MO is equal to the net energy destabilization due to the occupation of the corresponding antibonding MO.

Essentially, it claims that these two quantities are equal.

^{(Image source: SparkNotes)}

Shouldn't the antibonding orbital be destabilized more than the bonding orbital is stabilized, though?