What's your reasoning? Nowhere in the KS guidelines does it say you're not allowed to receive spam, only that you're not allowed to generate spam for your project. Please advise?

You should never engage a troll/netstalker. Ignoring them is the best approach, always. They feed on your engagement and get frustrated and go away looking for other targets if you ignore them.

If they become real-world stalkers, get a restraining order.