Dictionary.com - Dope
Webster Dictionary definition of Dope
3
a (1): an illicit, habit-forming, or narcotic drug; especially: marijuana (2): a preparation given to a racehorse to help or hinder its performance
I tried looking up an overly heated man named Carl on Miriam-Webster, but didn't find anything? Why? Because it's a real dictionary. Language is crazy... can you believe that the same word can mean different things to different groups of people? Nuts, right? One group using the word dope to refer to heroin does not mean that another usage is incorrect.
He's saying a fruit can be an apple, orange, or a pear, and you're telling him, "an apple is NOT a fruit, because an orange is". Just think on that.