If he has been kicked off 2 PhDs for the same thing, there is something wrong with management or they lack damning proof. pm133 is right, talk with other students if there is any evidence or collaborating stories and record them. You could make a long list of incidents that make it an unsafe work environment and that you want PhD students working in an area away from him.
Though if it is bad as you say it is with him getting away after repeated complaints, go through a different reporting structure. Maybe make your complaints directly to head of department or head of research, they will be less likely to know him and should be more fair.