Certainly Hannibal doesn't seem to have the self-preservation instinct that normally would prevent one from going off with strangers offering to buy the drinks. (Though it's hard to think of malicious reasons someone would have for luring him away; it's not like he owns anything worth stealing. Revenge for flirting with someone inappropriate? Some sort of class/religious/racial tension? Did someone tell him something he shouldn't know and they're trying to keep him from spreading the word? Or just mistaken identity?)