It's a test, you shouldn't have to sugar-coat explanations to an instructor (unless you're acting out some other scenario as part of the test).
You can argue that since the professor understood what was being said, the language shouldn't matter, but it does. If again you don't use the correct language you risk offending the listener so much he can't get past that. After all you are dealing with humans, not machines, and in either case you are responsible for clear communication.
However, life is very rarely optimal or fair. The only effect we can productively have on the world is through how we approach it, instead of focusing energy on how our actions are interpreted. It is unfortunate, but that is the most logical outcome. Focus on yourself, not on others.