Since an emblem is neither a card nor a permanent, and doesn't have a card type (as per rule 113.5, shown below), "has no name, no types, no mana cost, and no color" (rule 113.3, also below), and (as pointed out by murgatroid99) isn't even on the battlefield in the first place (rule 113.1, ... also below), is there any way to either nullify or destroy/exile it?
113.5. An emblem is neither a card nor a permanent. Emblem isn’t a card type.
113.3. An emblem has no characteristics other than the abilities defined by the effect that created it. In particular, an emblem has no name, no types, no mana cost, and no color.
113.1. Some effects put emblems into the command zone. An emblem is a marker used to represent an object that has one or more abilities, but no other characteristics.