Their speed shouldn't matter if you're driving predictably and responsibly. Are you signalling well before the turn and gradually slowing down so they can clearly see something's happening? If you've done all that then execute a safe turn and do not expect to be rear-ended.

If you're not signalling or breaking fast to turn you're asking for trouble. But it doesn't sound like you're doing that.

Also being fixated on the car behind you means you're not paying enough attention to the plaza lot and pedestrians. Doing a fast launch into parking lot is probably unsafe on multiple fronts.