What are you talking about? You presented the argument as a potential rebuttal to the claim that students cheat. It's inherently implied that it's an argument for the absence of cheating at Caltech... otherwise it wouldn't be a rebuttal at all, and instead is a non-sequitur fallacy.
Yes, if you strip away the context of the literal words you said, you're correct. But in context, you're not.
Yes, if you strip away the context of the literal words you said, you're correct. But in context, you're not.