I've had this happen to me as well. About a year ago, I saw some tail lights backing into my driveway. I looked out and and saw a car park in the middle of it, blocking me from getting out. The driveway is wide enough for two cars, my neighbor lives in NY now and lets me use his side as well, when he's in NY.
The guy parking his car in the middle got out, and started to walk to the duplex with garage apartment accross the street. There was plenty of room in the street to park. I asked him why he was parking in the driveway. He said his girlfriend lived in the garage apt. and that the rest of the people there didn't want him in their driveway. I told him he was blocking me in. No good. I told him it was my driveway. No good. It told him he could park on the street in front of my house. No good. I told him I was on call from work, and may have to leave at any moment. That got a response of "I'm only going to be here a couple of hours!"
Now I'm p*ssed off, and I assured him his car would be there less than that, as soon as I could get a tow truck and/or the police. He cussed me out, but moved the car.
And many houses around did not even have a car in the street in front of them. So, I got an idea how you feel. The nerve of some people. It's good you are staying calm, I'm glad I did, even though I was ticked.