General:
* Incitement
* Stimulation
* Elicitation
* Goading
* Instigation
* Triggering
* Arousal
* Enticement
* Temptation
* Inducement
More specific:
* Antagonism (if it leads to hostility)
* Abuse (if it involves verbal attacks)
* Harassment (if it is repeated and unwelcome)
* Baiting (if it is intended to draw a response)
* Aggression (if it is physically threatening)
* Threat (if it implies danger)
The best synonym will depend on the specific situation and the nuance you want to convey.