It's not that you weigh the options, pro and con, and choose the most appropriate behavior. It is instructive and binding, and the moral man feels compelled to heed his conscience. This is Torah. Were Torah brought to the world as a result of man's acceptance, he would view its commands as optional, subject to his approval. This is not so.
Man has no choice.
He ignores the Torah at his own peril. The Torah exists, and controls our world, like it or not. The Mitzvos of the Torah are not suggestions for good living, or opportunities to earn everlasting reward. They are imperatives of nature, the stipulations of existence. Here's an illustration.