Passive aggression often stems from underlying anger, sadness, or insecurity, of which the person may or may not be consciously aware. Passive-aggressive behavior may be an expression of those emotions or an attempt to gain control in a relationship.
Bearing that in mind can inform how you respond. Although it can be tempting to react by being passive-aggressive yourself, expressing anger or frustration will likely spur the person to continue behaving the same way. Demonstrating that you value the passive-aggressive person's perspective may help if you are thereby addressing an underlying sense of insecurity. But you should not apologize for unfounded offenses or otherwise placate them.
If at all possible, the best solution is often to limit the time you spend in their presence. But if you determine that confrontation is the best path forward, avoid being accusatory as you calmly explain how the behavior makes you feel.
