I love being swooped and harried by Magpies because their behaviour marks Springtime. (and the warmth is great cause to celebrate)
Out of the rest of the year, Magpies morph from a placid bird with a melodious song to one that becomes feisty, raucous, fierce: protective.
Occasionally, they will even draw blood, marking the season with flamboyant elan.
There are two good ways to handle swooping Magpies, both a good window to fear of whatever the type (It should be noted that Magpies will not swoop you if you are looking at them, if they can see your eyes):
Some of the hardier souls do nothing, simply continue walking on, aware of the peril, cognizant of possibility, but comfortable regardless;
An extension of this, some folk wear their sunglasses on back to front, as if they have eyes in the front and back of their head, aware of Magpie behaviour during nesting season and responding cleverly.
On the other hand, throwing stones at the swooping Magpie is definitely reactionary aggression and offers a window to ones relationship to many fears. (and one that will not likely deter the Magpie who is honed in on full nest, egg and hatchling protection mode regardless)