[Junior]

I would never kill anyone because of my morality, but if I had no morality, I might kill you for disagreeing with me if I felt like it and thought I would suffer no ill consequences to myself.

But you will suffer consequences. Your victim's family might come after you or your family. Your society might decide that you're too dangerous to keep around (you might kill one of them next).

[etlib]

Protagoras: I would never kill anyone because of my morality, but if I had no morality, I might kill you for disagreeing with me if I felt like it and thought I would suffer no ill consequences to myself.

Junior: But you will suffer consequences. Your victim's family might come after you or your family. Your society might decide that you're too dangerous to keep around (you might kill one of them next).

You would suffer consequences because you live in a society where the consequences exist. In some societies it is permissible to kill those with whom there is a disagreement. For example, the duel for honor.