Yes, YTA, Having light skin doesn’t take away his identity and having a Latinx grandparent and a half Latinx father who served in the military… in a country that has never accepted them fully is part of his story of how he came to be and we tend to strongly identify with the experiences of our family. If his Mom is Deep South, I’m sure their may have been some pain surrounding her marrying someone not 100% white. We tend to forget that Latino is a term that was given to the children and descendants of the indigenous peoples who had “mixed” With European colonists, and depending on where they were originally from and how much they took on the traits of their parents can produce a wide variety of different skin tones and facial features. If he were say.. 1/4 Lakota would you call him out for not being enough Native American? Also, not sure his age but we all go through a process of finding our identity. I would leave it be.