CAIR is asking political candidates scheduled to be at the event, such as Marco Rubio, to cancel their appearances unless Gabriel is dropped as a speaker.
In 2007, Gabriel gave a speech and said "between Israel and the Arab world is the difference between civilization and barbarism and also said of the "Arabic world," that they "have no soul."
Suggesting any peoples have "no soul" or are in some way less than human is to set up a justification for things like the talk-radio-fueled mass murder of Tutsis by Hutus in Rwanda, or the murder of Native Americans by us for centuries.