Answer:
He should wear what he wants to.
Step-by-step explanation:
There is no physical reason that Sean would be physically harmed by wearing what makes him happy. It would greatly help his young, impressionable independence to not conform to the opinions of others and see himself as an individual rather than a part of a single group. Ideas like this contribute to the foolishness of the process known as "Group Think" or the "Cheerleader Effect" in which humans will do what other humans do based on no benefit to themselves but the trust of humanity as a whole. This powers our dieting and fashion industry, and by conforming, Sean is contributing to this idea as a whole. For his future self's intelligence and confidence, he should wear what he wants to wear.