fuel the flame(s)

To do or say something to make an argument, problem, or bad situation worse; to further incense an already angry person or group of people. The debate was going poorly for the senatorial candidate, and his strikingly uncouth comments simply fueled the flames. Revelations of the CEO's massive retirement package fueled the flame for consumers already furious over the company's dubious financial dealings. Anything the mayor says will just fuel the flames, so do not let him speak to reporters about this sensitive issue.