I would say that spite-voting isn't a large enough problem to need a technical solution unless somebody's being hugely egregious, and if someone's being hugely egregious, there are admins that can step in, right?

There are admins that can step in, but I'm not sure if they have in past egregious cases. Aside from Will Newsome, I think there have been other significant instances of mass downvoting (at least PJ Eby, maybe others), and (correct me if I'm mistaken) I don't recall anything being directly done about either in the end, except the removal of voting buttons from userpages after Will brought it up. That was an improvement, but it's still clearly possible, and if someone were sufficiently motivated, it would be pretty easily scriptable.