I had a similar experience several years ago on the MTA. Guy asked for a dollar. I gave it to him, which made the new focal point in his life. He got in my personal space and was getting louder, venting his frustration at the world but kind of aiming it all at me. I could see other passengers looking at me with that, "See what happens?" look on their faces. I was getting desperate so I slowly unzipped my gym bag just enough to slide my hand inside and I left it there. All I had in there was workout gear but I guess it made him question whether I might have a weapon so I he shut up and moved on. I was definitely in a cold sweat and since then I don't even see them when they ask.