I wonder...
If Maria might have had something to do with it. Some California State legislator who had written or sponsored the bill the Governor vetoed had insulted Arnold. If I remember right, it had something to do with sticking something where the sun don't shine. Anyway, I would bet Maria has just enough devil in her to get a kick out of writing that and giving it to Arnold to send out.
But I could be wrong. It could be just a staffer. Or maybe we aren't giving Arnold enough credit.