They're a menace in that they do a hell of a lot of damage to the ecosystem with their trotters: Australian soil, in particular around waterholes and rivers, is so easily degraded by hoofed animals like cattle and pigs. This, in addition to the fact that they actively seek out and kill young lambs and other animals, will attack a human if provoked (and those tusks can disembowel) and they eat any crops or native plants that get in their way, make them a particular menace. Hence why pig-shooting is quite the leisure activity out in the sticks.