Basically it's sneaky, can hit anytime, you don't know how to find & target it, when it's going to attack, where it's going to come from, and what suffering it's going to cause (but you know it's going to be bad). It seems to me the metaphor is quite apt.

Personally, I didn't feel like the usage detracted from the article at all.

I'm not sure why it causes such a strong feeling of "hate". Mild disappointment perhaps, but hate?