The situation you describe is similar to that if you were on foot and walking. A hog comes past and you are in imminent danger of being run over. Even if there are other hogs around you can nade him, chances are you die, he dies and everyone is happy. It just makes sense that you can defend yourself - otherwise it wouldn't be fair.
It is unfortunate this player was trying to chase kill you. Obviously his intention to kill you was clear, as he kept coming back for more. Given the description of the event I certainly would not have warned you for camping, slayer or any other offense in the server. In this case you can do your best to keep yourself alive until you have no other option. The intent to race anda void bloodshed was there - just in this case not possible. As long as you keep these things in mind as I know you do you will do well. I wouldn't dwell on the situation too much, clearly he was far more trouble than you were!
