Legality of posting your photographs on the web (U.S.)

I posted this in the Open Forum as well but wanted opinions from here as well:

You take photos of a stranger in a very public place (tourist attraction) who is being photographed by another photographer. You find the photos interesting and post them for display on your web page. You are not marketing or selling the photos in question. The photographer contacts you after seeing your image of "his" shoot and demands that you remove them from your web page or face "legal action" because 1. you don't have a model release and 2. the subject is reportedly a minor. Your response is.......?--
'It is better to have and need not than to need and have not'