It is frustrating to be driving and have no idea what a cyclist is going to do. I have many drivers near me who are very courteous to cyclist. Unfortunately I have seen MANY roadies and Nest riding DUI types who feel no need to signal and simply pull into and out of traffic at the drop of a hat. That is VERY disconcerting, particularly if you are older or simply unprepared for it. I imagine that the driver you encountered had had this happen many times before. It becomes frustrating and they lash out. Be glad that he was aware of you, enough so to take notice of your intentions. If you can not safely signal while on your bike then you are either out of your comfort level or in above your head. At any rate you need to slow down, because at no point should you not be able to take basic safety measures and evasive maneuvers.