I don't think the OP was rude at all. She was coolly polite.
The guy's first comment sounds like a clumsy attempt at a joke. However, after DM said "I need all of them," the guy should have shut up or apologized. His comment "There's no way you need all of those" was overly personal and intrusive. He was putting her in a position where she either had to play along, or had to justify or explain her medical needs. (I don't think he thought for a minute that she was really a drug dealer.)
Etiquette doesn't require us to be friendly or encouraging to people who say boorish things. And sometimes people need to learn from experience that some kinds of jokes really aren't appropriate, at least not with people you don't know well.
Thank you for explaining that because that's how I see it. The first comment, okay, could have been a joke, so my "interesting assumption" was a "I'm not really sure how to respond to that...". It stopped being a joke when he started defending his initial boorish comment.
Also, I want to point out that accusing me of doing drugs in a stupid joke (per another thread about my necklace) and accusing me of being a drug dealer in a stupid joke are completely different things. Misdemeanor or felony? I also have a great sense of humor. Had someone said something like, "Whoa, looks like pharmacy in there!" I probably would have laughed and tried to push the Ibuprofen on them (jokingly, of course). Accusing me of engaging in felonious behavior during a Criminal Justice class
is just stupid, IMHO, and probably why I didn't find it funny at all. If I knew him better, was someone with whom I interacted, my response probably also would have been different. As I said above, my initial "interesting assumption" comment was more because I didn't have anything else to say. It was when he started defending himself that I felt it was not longer a joke and needed shut down.
As for it being heard getting to know people in class or joking around with a near stranger, that gives him no excuse to accuse of felonious behavior and I don't know why he would think that would be a good way to start off. I'm not saying that's what anyone here is implying, it was just a thought I had in response to a few different comments.
Isn't the point of this phrase to shut someone down when they're being rude? That's what I did and I don't think I did anything wrong at all. If this was not a good time to use this phrase then I don't know when is.