Most adults that I know have never used a straight razor or traditional safety razor blade before. In fact I think most couldn't even tell you the difference. I couldn't find safety razor blades at Target when I looked and bought them on Amazon. Everybody shaves with cartridge razors or electric razors these days. If you asked the average adult to draw a picture of a razor blade, I'd put money on the average response being a skinny blade as found in a cartridge (similar to a pencil sharpener) or a triangular knife blade like on an Exacto.

I would really encourage people not to draw conclusions based on the type of blade. It's just as likely to be a dumbass adult that doesn't know the difference, a regular ass adult that doesn't care about the difference, an adult that thinks he's smart and trying to act as if he thinks a kid might act, or an actual kid.