Otherwise, generally speaking, the objective, known-to-all course of study is "learn things, answer the questions, pass the test". Which means it doesn't matter if you already saw the answer. It's not uncommon for students to go into tests knowing some of the answers already, either directly or through simple experiential logic.
(Some systems have a clause though, which is e.g. "if somebody else gave you the answer with the aim of helping you pass the test without needing to learn, then that's cheating and you should not do it.")
Also, if the first line above is definitely not true, you'll generally be punished for revealing it. At a minimum it'll look like:
- Critique: You are criticizing the quality of their work, when this is not really why you were asked there.
- Know-it-all syndrome: You are showing off.
- Morality crusader / morality porn: You are mainly focused on how good of a person you can be, in terms of being a "quality human," etc.
So, quite often the more objective social messaging system is not working in your favor and will not understand the point of your sharing this information. The confusion will lead to you being labeled as conveniently as possible.
You could even look effectively immoral for bringing it up, whether you knew the answer or not.
If you find yourself continually coming around to this question, it may help to study personality theory for more information on this qualitative-morals perception, how various people may see it, etc.
There's also the question of how you'd phrase the issue, & what your issue with it is and how that's presented.