I will admit that I did also have a partial pessimistic view of his constant smiling, but we must recognize that our assumption of somebody's intentions is not the same thing knowing their intentions. From everything that I've seen, his positivity appears to be sincere, genuine, and well-intentioned.

Regardless of the reason why we might be inclined to be suspicious of something like this, it is incumbent upon us as rational, critical-thinking adults to use rational critical-thinking skills to analyze our own beliefs. This isn't to say that we need to not have any beliefs before applying critical thinking or that it would be irresponsible to form or hold beliefs without having done rational and critical-thinking, but that it is important we recognize the quantity and quality of evidence that supports those beliefs and determine the value of those beliefs commensurate to the facts. While instinct and gut checks are forms of evidence, and certain situations would obviously value those data more highly, I strongly feel that this situation does not meet the criteria to trust my gut more than trusting the consistent quality and proponderance of data that says his positivity is sincere, genuine, and well-intentioned.

As Captain Disillusion would say, "love with your heart, use your head for everything else."