Trying to hide is asking for confrontation, people can see when someone is being sneaky and it makes everyone else nervous as well. No one will care if your honest about what your doing, don't hide the camera that's ridiculous and its hard to get anything with any camera if your not looking through the viewfinder. You might get "don't take my photo again," but why would you, you already got the shot you wanted. Stop thinking about what will be said afterwards. If someone asks if you took their photo, say "Yes." That's all. If they ask why, say "for art." I picked that up from someone else (I don't remember who now). They won't ask another.
There's only taking a photo and not taking a photo, don't think, just do.