I don't think the Magpies would kill a lizard but it's a possibility. They don't like them because like snakes they will eat eggs. Unlike snakes they are rotten climbers though so nestlings are usually safe from lizards.
Magpies, apart, oddly, those from Tasmania, will swoop during the breeding season as they are fiercely territorial around their nests. It is not uncommon at this time of year to be riding your motorcycle down a suburban street and suddenly you get whacked on the back of the helmet by a swooping Maggie! Cyclists adorn their helmets with cable ties to defend themselves which is why you may of seen slightly puzzling pictures of Australian Lycra Louts with headgear that looks like a porcupine! They, (Magpies, not Lycra Louts.) have been known to peck people's eyes out but this is very rare.
We have a family that have lived in the big Cyprus Pine at the back of our place for years, (Individuals can live to be 25-28 years old!) and we never have any problems because we are friends of Magpie-kind and feed them kitchen scraps and cat food, (Not a lot as it isn't good for them and stops them foraging because like every other creature they are as lazy f*@&.) so they think we're wonderful
They have a wonderful warbling song that is a joy to listen to so we thoroughly enjoy having them around.
The Currawongs!? Now they're just plain nasty!
Pete