Love that sign. And do they have to be big rocks? It is hard to carry very many if they are large, but seems you need a bit of heft to bounce off and make a proper statement. And I do like the idea of babble to throw another off. Must try that. Next time someone in line at the bank is making no sense or butting into line.
My patented communication move is misdirection via absurdity. It works really well when someone is going to blow up at you, or you don't know how to get them what they require, or you just aren't overly fond of someone's behavior. It really is an all around tool to have in one's human interaction arsenal. I make my boss laugh daily with its utilization. On purpose of course. heh.
Regarding rock size, I would feel that as long as one's aim was fairly decent, that you wouldn't need to burden yourself unduly. Then again, if I ever see a shape-shifter, I would probably ask it something rather absurd without speaking and forget that I even have ammo of repellent nature.
Good on ya for the absurdity misdirect. I've always thought these sorts of things or self deprecation will get you far in life, or at least deflect alot of bad stuff coming your way. How can they take you serious, if you're not serious?
I'm rather worried about your safety here. Forgetting all about your rock ammo in this situation is not a good thing. Though very realistic. I'm pretty sure if I saw a shapeshifter in my closet, it would be worse than seeing a shark in deep water away from the boat. Just kind of gulp away in the snorkel and hope the old ticker keeps on working long enough to get away. Bonking one of those things on the head with a stone would only make it mad, which might not be a good thing in an enclosed closet.