You teacher may have taught you to answer questions with a "complete sentence" — i.e. not to start your ansswer with because if the question asked why, and generally to repeat the presupposed parts of the question in your answer.
Most of what it taught in those lessons is garbage — linguistically, the concept of a "complete sentence" is largely meaningless, and forbidding naturalistic answers to questions in a pedagogical context just creates busywork that makes students hate school while teaching them nothing.
However, there is a tiny kernel of truth to the idea, which can become crucially important in political discussions:
When you respond to a claim made by another person about a potentially sensitive topic, it is a good idea to repeat the claim that you think the person made in your response. That way, your readers will have the appropriate context for the message that you yourself are trying to convey, which may not be the same as the context they would have been working with given only their own reading of the original post. They are also more likely to notice (and to forgive you) if you misread the original poster and thus misinterpreted what they are saying.
In a political context, fully elaborating what you mean and the position you are taking when responding to somebody else is essential, because it helps avoid gaffes — situations where you e.g. respond positively to something that looks nice on the surface, but turns out to be a dog whistle.
More generally, if you take the time to say what you mean instead of assuming that what you meant was also what the person meant, you are a tiny bit less likely to find that you have accidentally said something awful.