I've been feeding a few magpie families for over 12 months now - yes, I love them. I appreciate people are upset/scared/frustrated with attacking magpies - my theory is that they get territorial if they have a food source in the area - they think you want to steal their food.
I have one male who keeps attacking other young magpies - picking one in particular - and he was quite vicious with it! It broke my heart listening to her screams - so I waited with a spray bottle of water and squirted him whenever the young one was around.
He still tries to intimidate the other magpies but is very wary of me - BUT still comes around for a feed. Even with all this, he NEVER attacked me.
Food is the secret. They love mince, about the size of a pigeon egg is enough. Researchers have found if someone in the neighbourhood feeds them the attacks stop. I appreciate the fear people have, but it breaks my heart to read how people are attacking magpies - they look the same - I don't know how people can be sure to be picking the attacker.