I think you overreacted. Someone showing an interest in photography and starting to start a conversation is a good thing to me. If he disrupted your work, there is nothing wrong with 'give me a minute till I have that shot taken' and then answer their question and maybe kindle some excitement in that person to bring a camera next time around.
Also what is the issue with people taken the same photo as you do? You are taking the image for you and not for the purpose of being the only one. When I started out in photography many a few decades ago, I would also try and learn from more experienced photographers and getting the best composition out of the scene is one of those things. I am sure you are a great photographer, so take it as a compliment that others want to take the same image that you just took.
To me photography is a passion that I love sharing with others and if I can help someone get a better picture and give them some assistance, I am happy to do it, because there were tons of photographers doing the same for me.
Just my two cents ...