The Collaborative International Dictionary of English v.0.48:

instigative \instigative\ adj.
   arousing to action or rebellion.

   Syn: incendiary, incitive, inflammatory, rabble-rousing,
        seditious.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

instigative
    adj 1: arousing to action or rebellion [syn: incendiary,
           incitive, inflammatory, instigative, rabble-
           rousing, seditious]