Had a couple of similar situations recently. It’s tough, cause it can really get you questioning your motivations and ethics. I find that aspect of a confrontation good. I need to be more mindful of what I’m doing (at least at the outset), and should be able to make a confident defense, should I be questioned. The bad part is…I don’t like confrontation. It makes me feel like I’ve wronged someone, and have maybe ruined their day or changed their perspective for the worse. In the end, I do not have any control over how people react, and I try to keep that in mind (I do not own others insecurities and I am not out to do harm).
The “delete the picture” is a little tough when you’re shooting film. The best I can do is say (sincerely) “sorry” and move on as quickly as possible. (This is also why It’s REALLY hard for me to shoot unannounced on a bus/train, where I’ve had a few confrontations).
After that, it’s best to get some better encounters in ASAP. Like: talk to an many people as you can find and try to get some good shots with them.