I think the issue is less the chance of the lawnmower going wild by itself (because screw that, I don't care how small the chance is, it's not acceptable), and more the chance of the lawnmower exploding, taking out your eye when you trigger it's failure it yourself.
As in, "the chance of getting hacked" < "the chance of the vigilante creating dangerous situations".
As in, "the chance of getting hacked" < "the chance of the vigilante creating dangerous situations".