Is it customary to call kids stupid in your culture?

*****Additional Info: I am currently dating a Nigerian man and we have a newborn together. I also have a son from my previous marriage and he called him stupid. I was outraged and disgusted and he said that it’s not uncommon for kids to be called stupid in his culture and that ultimately it just means disrespectful. Not sure I’m buying it so I wanted some input from others that are from the culture. Thanks