I agree that they should be treated like human beings because they are. if a celeb is visibly uncomfortable or is clearly not looking their best, leave. but if you ask them for a photo and they say yes then they can't really complain.
like I agree that shoving your face right next to them and snapping a selfie without asking is incredibly disrespectful... but as long as people ask I don't see the issue tbh.
The thing is that the artist should be the one to allow it and if they dont feel like doing it they don't owe anything to the fans. Usually M&G are a thing for that.(Justin doesnt do it but irrelevant to the current talk)