I don’t know what to tell you other than I honestly did not know the OK thing was a WP sign, so how the heck can I expect everybody else does, either?
I’m fairly well-read and educated, so I’m willing to give benefit of the doubt that if I don’t know something it’s entirely possible a 16 year old doesn’t either.
If, after investigating, it turns out he’s the one that carved the Nazi insignia into a desk then of course that will be powerful proof that he’s into WP. Until I have a little more info, though, I’m hesitant to condemn or label a 16 year old for something that there’s not universal agreement or knowledge of.