I guess that: "You fool! It is not a picture. Take a picture using supplied UI widget that resides in place where one would expect software keyboard." sounds less appealing to teenagers :)
It's not a pic fool. Take a pic from the keyboard!
It's calling you a fool for sending something that isn't a pic. The way I understood it it's also telling you to take a pic from the in-app keyboard but I haven't actually tried it so I can't confirm this.