[xiju]

I think your neighbour is continuing with the "rat" comments because it seems to bother you. Instead of making bad friends, could you maybe ask him in a nice way to stop? Something like "I really wish you'd stop with the rat jokes because it hurts my feelings. If we are to remain friends, I'd prefer you just stop!". I'd go that route before starting a war. It might be a lot more pleasant in the end. Best of luck and congratulations on your graduation.