Ha ha--sorry, but I think it's hilarious that he only paid you two bucks and still thinks it's appropriate to b*tch. That's a heck of a deal, even if all he was going to do was eat them.
It sounds to me like he is looking for a fight. Frankly, if it were me, I'd just refund the money and put him on my blacklist. That's how I do business with my writing too--when I discover a client who is just plain unpleasant to deal with, I stop invoicing, tell him "thank you very much" and add him to my database of people I never work with again. I don't, however, actually issue refunds, but in the case of a $2 charge, I probably would.
But, anyway, that's probably not really what you need to hear. Even if it is just $2, it's not fun to receive nasty emails, especially when you have done the right thing and been conscientious and put effort into the deal. He's out of line, and you have acted honorably. Everyone here knows that shipping is a gamble, no matter how careful the seller is.
Good luck with whatever comes next. My guess is that he will probably still want to fight--he'll want to argue with your defenses and tell you how much experience he has and that you're rude to question his incubation processes and so on. Just remember that this is about his issues, not yours. Keep cool and do what's right for you. And I'm sorry you have to deal with it.