My two cents (personal opinion)...
If you're being honest with yourselves, fighting on the streets is not the most honorable thing a person could do, martial artist or no. Neither is training to hurt/maim/kill someone regardless of the reason.
People shouldn't have to get their morals from an "art" which is designed to hurt others. That would be like studying to be a dietician at the University of McDonald's. (No relation to this website stated or implied whatsoever, hummana hummana...)
Unless your school is an organization like the Shaolin Temple, for example, that blends "religion" (Buddhism isn't technically a religion in the Western sense) and martial skill, or an organization that has a specific purpose for martial arts (Police Force, Military, etc), then as individuals, it's not the responsibility of the instructor to teach you morals. In the above cases, morals are needed because each member of the "team" or each disciple at the temple is an integral part of a group working toward a goal. If there were no ground rules (codes of honor, for example) the group could not succeed.
But your average Dojo in the U.S, at least, doesn't need all that. People go there to train a few days a week, and then go home to their jobs and their lives. If one of them doesn't show up, the school goes on (or goes under if they're not getting enough business...) and nobody cares. If they use their skills to rob an old lady, they are individually responsible for their own actions, being private citizens.