As a landscape photographer, the behaviour of a few street photographers can be quite confronting and odd. My personal experience is that a few of them can be quite intrusive and overbearing. If that's the case, I turn my back — and they move on to their next subject. I often ask myself, "why photograph me?" "What's so special about me?". I have witnessed confrontations where cameras have been grabbed and hurled (!). I don't think it's a question totally of ethics, but with significant elements of respect and courtesy. A photographer is nothing special, and like his subject(s), is not afforded any protection, especially if there is a legal case eventuating from his/her activities when he/she could well be asked to justify his actions.
Now, regarding rights [to privacy in public], implied or otherwise, have a read of this (below), the law from the Australian perspective. The final paragraph may also hold true for other countries (UK, US?) -- I don't know, but photographers should have an effective working grasp of the law as it stands, especially when visiting other countries where the law could be quite different.
[ from http://www.artslaw.com.au/images/uploads/Street_photographers_rights_2016.pdf ]
Street Photographer’s Rights
Can I take a photograph in public that contains images of people I don’t know?
[...]
Taking photographs in a public place
It is generally possible to take photographs in a public place without asking permission. This
extends to taking photographs of buildings, sites and people. In a case involving street surveillance photography used as evidence in a criminal case,
an Australian judge stated “a person, in our society, does not have a right not to be photographed.”
[limitations to this statement omitted for brevity here]
Some photographers have been approached by the police while on the street taking photographs.
The police are usually responding to a complaint by some member of the public who is concerned about children being photographed and who have a mistaken belief that the consent of the parents or guardian must be obtained before children can be photographed. Street photographers should be prepared to respond to this situation, either by acknowledging the concerns of the parents and adopting appropriate strategies, such as explaining what you are doing and asking it is OK to take photographs; or otherwise have the information on street photographer’s rights so that you can have a conversation in which you explain what you are doing and why you have a right to engage in street photography.
Photographing people
There are no publicity or personality rights in Australia, and there is no right to privacy that protects a person’s image. However a person’s image can constitute ‘personal information’ under the
Privacy Act 1988 (Cth) [...]