That makes perfect sense for a four year old. It also revealed what was important to him, for example, superheroes are currently his mentors, he is interested in that job possibility in the future and wants to prepare for that eventuality now, and obviously he is thinking of his future and wearing a "blue ear" didn't fit his vision.
Anthony's Mom apparently was not an expert on superheroes so she wisely consulted with someone who was. She emailed Marvel comics and ask if there was a hearing impaired hero and they responded that Hawkeye was indeed hearing impaired.
But Marvel didn't stop there and before they were done they sent some drawings as you can see below.
Isn't it nice that people can come through for others once in a while? Isn't great that a company that exists to make money and produce entertainment can see more than the masses and can see the needs of one little boy and come through for him? And that Super Heroes not only sometimes need a hearing aid but that every super hero needs a Mom to lead him in the right direction? Hurray for Mom's who help us find reasons why we CAN reach our potential instead of let us be satisfied with reasons that keep us from being our best selves. Thanks Mom!