I had an issue while me and my wife were in London at the weekend, we were just doing the tourist thing, walking around and seeing the sights, I took my Hasselblad X2D II with me, it wasn't a photography trip so I was only taking general snaps really.
While my wife was taking a shot of Big Ben I took a picture of people walking part a tourist stand opposite Westminster, and I noticed the guy was giving me a single finger, then put 2 fingers up and then his wife started screaming at me, so I walked over to speak to them.
I was met with instant abuse, "You're breaking the law, it's illegal for you to take our picture without our consent, delete them now", I tried to calmly explain that as I am standing in a public place I don't need permission to take any pictures, they pointed to a sign they have that said no photography was allowed, they wouldn't listen to me so I pulled Google up and showed them a web page from Metropolitan Police that explains it's legal, they changed stance then saying it was immoral. Ended up with the guy saying he wasn't too old to come out of his stand and have a 'straightener' with me, pretty pathetic really, I just told him to have a nice day and walked away.
They couldn't understand the irony that they don't want to appear in any pictures yet they are stood by one of the photographed spots in London.