I'm 18 years old. I'm not white and certainly have a different upbringing from Hader, but I still feel as though a 17 year old should understand what "white power" means. I can see why an unwise kid would think of it as a joke, but at 17, it's really hard for me to believe that he could be that dumb and not know what the phrase means.
I know that kids his/my age joke around with these phrases, for sure, but tweeting it with no context is different, and worse