Several things to consider from both a historical and a personal perspective on that image.
Firstly, in such times water was rather dangerous to drink. Without a proper way of cleaning or sanitizing a water supply, any beverage made directly from water would yield dangerous results. Ben Franklin would suffer a chance of shitting out his own insides if he were to take a drink from that Kool-aid man. Ideally the beverage would actually have to have been made from some form of clear alcohol for it to really be safe for Franklin to drink while retaining the crisp, cherry flavor of Kool-aid. Of course, such a mixer would lead Kool-aid away from it's kid-appropriate, family image.
Secondly, Franklin's more appropriate response should be "OH HOLY SHIT A GIANT TALKING PITCHER OF RED LIQUID! WHAT THE FUCK?"