You make your argument, your opponent makes his, and whoever persuades a jury or a judge wins.
Whether you argument is logically correct, meets the facts or the law, or is just is completely irrelevant apart from whether the judge or jury finds you persuasive.
The fact that we, as a society, turn over so much authority to people trained to be paid liars is a big problem.
So what law school did you attend that gave you this knowledge of what is taught in law school?
Because mine was nothing like that. In fact, tons of people go through law school and don't study trial work at all.