Well couldn't you just say that the another cup that thinks it's lemonade is an optimist, assuming we don't really know what said liquid is? Which I assume must be true because neither of the other cups seem to notice, and the third cup is only speculating. Furthermore, even if it was piss why is that necessarily a bad thing? Could be that they're piss tests to keep drug addicts from leaving rehab, or some type of new scientific research. In which case the optimist is in better standing to deal with reality since he doesn't let a petty thing like being filled with piss distract him from the noble goals that got him there in the first place. Overall I give this cartoon a pessimistic bias, the realist isn't really necessarily poor when you think about it.